Page 1
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 1
Date : 5
th
September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Maths
Q.1 If x=1 is a critical point of the function f(x)=(3x
2
+ax–2–a)e
x
, then:
(1) x=1 is a local minima and
2
x
3
? ? is a local maxima of f. .
(2) x=1 is a local maxima and
2
x
3
? ? is a local minima of f. .
(3) x=1 and
2
x
3
? ? are local minima of f. .
(4) x=1 and
2
x
3
? ? are local maxima of f. .
Sol. 1
f(x) = (3x
2
+ax–2–a)e
x
f
’
(x) = (3x
2
+ax–2–a)e
x
+ (6x+a)e
x
= 0
? ?
x 2
e 3x a 6 x 2 ? ? ? ? ?
? ?
=0
at x = 1, 3 +a+6 - 2 = 0
a=–7
f(x) = (3x
2
- 7x + 5 )e
x
f
’
(x) = (6x—7)e
x
+(3x
2
-7x+5)e
x
= e
x
(3x
2
-x-2) = 0
= 3x
2
—3x + 2x - 2 = 0
= (3x+2) (x—1) = 0
x = 1, -2/3
+ – +
–2/3
1
x = 1 is point of local minima.
x = –2/3 is point of local maxima.
Q.2
? ?
2 4
1 x x 1 x
1
x 0 2 4
x e
1 x x 1
/
lim
? ? ?
?
?
? ?
? ?
? ?
? ? ?
(1) is equal to
e
(2) is equal to 1 (3) is equal to 0 (4) does not exist
Sol. 2
? ?
? ?
2 4
1 x x 1 /x
x 0 2 4
x e 1
lim
1 x x 1
? ? ?
?
? ?
?
? ?
? ?
? ? ?
Page 2
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 1
Date : 5
th
September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Maths
Q.1 If x=1 is a critical point of the function f(x)=(3x
2
+ax–2–a)e
x
, then:
(1) x=1 is a local minima and
2
x
3
? ? is a local maxima of f. .
(2) x=1 is a local maxima and
2
x
3
? ? is a local minima of f. .
(3) x=1 and
2
x
3
? ? are local minima of f. .
(4) x=1 and
2
x
3
? ? are local maxima of f. .
Sol. 1
f(x) = (3x
2
+ax–2–a)e
x
f
’
(x) = (3x
2
+ax–2–a)e
x
+ (6x+a)e
x
= 0
? ?
x 2
e 3x a 6 x 2 ? ? ? ? ?
? ?
=0
at x = 1, 3 +a+6 - 2 = 0
a=–7
f(x) = (3x
2
- 7x + 5 )e
x
f
’
(x) = (6x—7)e
x
+(3x
2
-7x+5)e
x
= e
x
(3x
2
-x-2) = 0
= 3x
2
—3x + 2x - 2 = 0
= (3x+2) (x—1) = 0
x = 1, -2/3
+ – +
–2/3
1
x = 1 is point of local minima.
x = –2/3 is point of local maxima.
Q.2
? ?
2 4
1 x x 1 x
1
x 0 2 4
x e
1 x x 1
/
lim
? ? ?
?
?
? ?
? ?
? ?
? ? ?
(1) is equal to
e
(2) is equal to 1 (3) is equal to 0 (4) does not exist
Sol. 2
? ?
? ?
2 4
1 x x 1 /x
x 0 2 4
x e 1
lim
1 x x 1
? ? ?
?
? ?
?
? ?
? ?
? ? ?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 2
? ?
? ?
? ?
2
2 4
1 x x 1
x 2
2 4
2 4
x 0
x e 1 1 x x 1
lim
x x
? ?
? ? ? ? ?
? ?
? ? ?
? ?
? ?
?
? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
? ?
?
? ?
?
? ?
? ?
? ?
?
?
?
? ? ?
?
? ?
? ?
3
x x
2
3 x 0
e 1
lim 2
x x
2
2
= 1
Q.3 The statement p q p p p q ( ( )) ( ( )) ? ? ? ? ? is:
(1) equivalent to p q p ( ) (~ ) ? ?
(2) equivalent to p q p ( ) (~ ) ? ?
(3) a contradiction
(4) a tautology
Sol. 4
? ? ?
? ? ? ? ? ?
? ?
(p (q p))
p q q p p (q p) p q p p q
(p (p q))
T T T T T T T
T F T T T T T
F T F T T T T
F F T T F T T
Q.4 If
2 2
L
16 8
sin sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
and
2 2
M
16 8
cos sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
, then:
(1)
1 1
M
2 8
2 2
cos
?
? ?
(2)
1 1
M
4 8
4 2
cos
?
? ?
(3)
1 1
L
2 8
2 2
cos
?
? ? ?
(4)
1 1
L
4 8
4 2
cos
?
? ?
Sol. 1
L =
? ? ?
? ?
? ?
3
s in
1 6
sin
16
? ? ? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
1
L cos cos
2 8 4
?
1
L
2 2
—
1
cos
2 8
?
Page 3
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 1
Date : 5
th
September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Maths
Q.1 If x=1 is a critical point of the function f(x)=(3x
2
+ax–2–a)e
x
, then:
(1) x=1 is a local minima and
2
x
3
? ? is a local maxima of f. .
(2) x=1 is a local maxima and
2
x
3
? ? is a local minima of f. .
(3) x=1 and
2
x
3
? ? are local minima of f. .
(4) x=1 and
2
x
3
? ? are local maxima of f. .
Sol. 1
f(x) = (3x
2
+ax–2–a)e
x
f
’
(x) = (3x
2
+ax–2–a)e
x
+ (6x+a)e
x
= 0
? ?
x 2
e 3x a 6 x 2 ? ? ? ? ?
? ?
=0
at x = 1, 3 +a+6 - 2 = 0
a=–7
f(x) = (3x
2
- 7x + 5 )e
x
f
’
(x) = (6x—7)e
x
+(3x
2
-7x+5)e
x
= e
x
(3x
2
-x-2) = 0
= 3x
2
—3x + 2x - 2 = 0
= (3x+2) (x—1) = 0
x = 1, -2/3
+ – +
–2/3
1
x = 1 is point of local minima.
x = –2/3 is point of local maxima.
Q.2
? ?
2 4
1 x x 1 x
1
x 0 2 4
x e
1 x x 1
/
lim
? ? ?
?
?
? ?
? ?
? ?
? ? ?
(1) is equal to
e
(2) is equal to 1 (3) is equal to 0 (4) does not exist
Sol. 2
? ?
? ?
2 4
1 x x 1 /x
x 0 2 4
x e 1
lim
1 x x 1
? ? ?
?
? ?
?
? ?
? ?
? ? ?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 2
? ?
? ?
? ?
2
2 4
1 x x 1
x 2
2 4
2 4
x 0
x e 1 1 x x 1
lim
x x
? ?
? ? ? ? ?
? ?
? ? ?
? ?
? ?
?
? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
? ?
?
? ?
?
? ?
? ?
? ?
?
?
?
? ? ?
?
? ?
? ?
3
x x
2
3 x 0
e 1
lim 2
x x
2
2
= 1
Q.3 The statement p q p p p q ( ( )) ( ( )) ? ? ? ? ? is:
(1) equivalent to p q p ( ) (~ ) ? ?
(2) equivalent to p q p ( ) (~ ) ? ?
(3) a contradiction
(4) a tautology
Sol. 4
? ? ?
? ? ? ? ? ?
? ?
(p (q p))
p q q p p (q p) p q p p q
(p (p q))
T T T T T T T
T F T T T T T
F T F T T T T
F F T T F T T
Q.4 If
2 2
L
16 8
sin sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
and
2 2
M
16 8
cos sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
, then:
(1)
1 1
M
2 8
2 2
cos
?
? ?
(2)
1 1
M
4 8
4 2
cos
?
? ?
(3)
1 1
L
2 8
2 2
cos
?
? ? ?
(4)
1 1
L
4 8
4 2
cos
?
? ?
Sol. 1
L =
? ? ?
? ?
? ?
3
s in
1 6
sin
16
? ? ? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
1
L cos cos
2 8 4
?
1
L
2 2
—
1
cos
2 8
?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 3
M =
3
cos
16
? ? ?
? ?
? ?
cos
16
? ? ?
? ?
? ?
M =
1
cos cos
2 4 8
? ? ? ?
?
? ?
? ?
M =
1
2 2
+
1
2
cos
8
?
Q.5 If the sum of the first 20 terms of the series
? ? ? ? ? ?
1 2 1 3 1 4
7 7 7
x x x
/ / /
log log log ... ? ? ? is 460,
then x is equal to:
(1) 7
1/2
(2) 7
2
(3) e
2
(4) 7
46/21
Sol. 2
(2 + 3 + 4 +... + 21)log
7
x = 460
? ?
? ?
7
20 21 2
log 460
2
? ?
? x
? ?230 log
7
x = 460 ? log
7
x = 2 ? ?x = 7
2
Q.6 There are 3 sections in a question paper and each section contains 5 questions. A
candidate has to answer a total of 5 questions, choosing at least one question from
each section. Then the number of ways, in which the candidate can choose the questions,
is:
(1) 2250 (2) 2255 (3) 1500 (4) 3000
Sol. 1
S—1 S—2 S—3
1,2,3,4,5 1,2,3,4,5 1,2,3,4,5
6 case
1
1
1
2
2
3
1
2
3
2
1
1
3
2
1
1
2
1
= 3(
5
C
1
×
5
C
2
×
5
C
2
) + 3(
5
C
1
×
5
C
1
×
5
C
3
)
= 3(5 × 5 × 2 × 5 × 2) + 3(5 × 5 × 10)
= 750 + 1500 = 2250
Q.7 If the mean and the standard deviation of the data 3,5,7,a,b are 5 and 2 respectively,
then a and b are the roots of the equation:
(1) x
2
–20x+18=0 (2) x
2
–10x+19=0 (3) 2x
2
–20x+19=0 (4) x
2
–10x+18=0
Sol. 2
S.D. =
? ?
2
2
i
x
x
n
?
?
Page 4
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 1
Date : 5
th
September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Maths
Q.1 If x=1 is a critical point of the function f(x)=(3x
2
+ax–2–a)e
x
, then:
(1) x=1 is a local minima and
2
x
3
? ? is a local maxima of f. .
(2) x=1 is a local maxima and
2
x
3
? ? is a local minima of f. .
(3) x=1 and
2
x
3
? ? are local minima of f. .
(4) x=1 and
2
x
3
? ? are local maxima of f. .
Sol. 1
f(x) = (3x
2
+ax–2–a)e
x
f
’
(x) = (3x
2
+ax–2–a)e
x
+ (6x+a)e
x
= 0
? ?
x 2
e 3x a 6 x 2 ? ? ? ? ?
? ?
=0
at x = 1, 3 +a+6 - 2 = 0
a=–7
f(x) = (3x
2
- 7x + 5 )e
x
f
’
(x) = (6x—7)e
x
+(3x
2
-7x+5)e
x
= e
x
(3x
2
-x-2) = 0
= 3x
2
—3x + 2x - 2 = 0
= (3x+2) (x—1) = 0
x = 1, -2/3
+ – +
–2/3
1
x = 1 is point of local minima.
x = –2/3 is point of local maxima.
Q.2
? ?
2 4
1 x x 1 x
1
x 0 2 4
x e
1 x x 1
/
lim
? ? ?
?
?
? ?
? ?
? ?
? ? ?
(1) is equal to
e
(2) is equal to 1 (3) is equal to 0 (4) does not exist
Sol. 2
? ?
? ?
2 4
1 x x 1 /x
x 0 2 4
x e 1
lim
1 x x 1
? ? ?
?
? ?
?
? ?
? ?
? ? ?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 2
? ?
? ?
? ?
2
2 4
1 x x 1
x 2
2 4
2 4
x 0
x e 1 1 x x 1
lim
x x
? ?
? ? ? ? ?
? ?
? ? ?
? ?
? ?
?
? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
? ?
?
? ?
?
? ?
? ?
? ?
?
?
?
? ? ?
?
? ?
? ?
3
x x
2
3 x 0
e 1
lim 2
x x
2
2
= 1
Q.3 The statement p q p p p q ( ( )) ( ( )) ? ? ? ? ? is:
(1) equivalent to p q p ( ) (~ ) ? ?
(2) equivalent to p q p ( ) (~ ) ? ?
(3) a contradiction
(4) a tautology
Sol. 4
? ? ?
? ? ? ? ? ?
? ?
(p (q p))
p q q p p (q p) p q p p q
(p (p q))
T T T T T T T
T F T T T T T
F T F T T T T
F F T T F T T
Q.4 If
2 2
L
16 8
sin sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
and
2 2
M
16 8
cos sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
, then:
(1)
1 1
M
2 8
2 2
cos
?
? ?
(2)
1 1
M
4 8
4 2
cos
?
? ?
(3)
1 1
L
2 8
2 2
cos
?
? ? ?
(4)
1 1
L
4 8
4 2
cos
?
? ?
Sol. 1
L =
? ? ?
? ?
? ?
3
s in
1 6
sin
16
? ? ? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
1
L cos cos
2 8 4
?
1
L
2 2
—
1
cos
2 8
?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 3
M =
3
cos
16
? ? ?
? ?
? ?
cos
16
? ? ?
? ?
? ?
M =
1
cos cos
2 4 8
? ? ? ?
?
? ?
? ?
M =
1
2 2
+
1
2
cos
8
?
Q.5 If the sum of the first 20 terms of the series
? ? ? ? ? ?
1 2 1 3 1 4
7 7 7
x x x
/ / /
log log log ... ? ? ? is 460,
then x is equal to:
(1) 7
1/2
(2) 7
2
(3) e
2
(4) 7
46/21
Sol. 2
(2 + 3 + 4 +... + 21)log
7
x = 460
? ?
? ?
7
20 21 2
log 460
2
? ?
? x
? ?230 log
7
x = 460 ? log
7
x = 2 ? ?x = 7
2
Q.6 There are 3 sections in a question paper and each section contains 5 questions. A
candidate has to answer a total of 5 questions, choosing at least one question from
each section. Then the number of ways, in which the candidate can choose the questions,
is:
(1) 2250 (2) 2255 (3) 1500 (4) 3000
Sol. 1
S—1 S—2 S—3
1,2,3,4,5 1,2,3,4,5 1,2,3,4,5
6 case
1
1
1
2
2
3
1
2
3
2
1
1
3
2
1
1
2
1
= 3(
5
C
1
×
5
C
2
×
5
C
2
) + 3(
5
C
1
×
5
C
1
×
5
C
3
)
= 3(5 × 5 × 2 × 5 × 2) + 3(5 × 5 × 10)
= 750 + 1500 = 2250
Q.7 If the mean and the standard deviation of the data 3,5,7,a,b are 5 and 2 respectively,
then a and b are the roots of the equation:
(1) x
2
–20x+18=0 (2) x
2
–10x+19=0 (3) 2x
2
–20x+19=0 (4) x
2
–10x+18=0
Sol. 2
S.D. =
? ?
2
2
i
x
x
n
?
?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 4
(2)
2
=
2 2
83 a b
5
? ?
—(5)
2
4 =
2 2
83 a b
5
? ?
— 25
29×5 — 83 = a
2
+b
2
? a
2
+b
2
= 62
a b 15
5
? ?
= 5
? a b 10 ? ? ...(1)
2ab = 100 — 62 = 38
ab 19 ? ...(2)
from eq.(1) & (2)
x
2
– 10x + 19 = 0
Q.8 The derivative of
2
1
1 x 1
x
tan
?
? ?
? ?
? ?
? ?
? ?
with respect to
2
1
2
2x 1 x
1 2x
tan
?
? ?
?
? ?
? ?
?
? ?
at
1
x
2
? is:
(1)
2 3
3
(2)
2 3
5
(3)
3
12
(4)
3
10
Sol. 4
x = tan ?
u =
1
sec 1
tan
tan
?
? ? ? ?
? ?
?
? ?
= ? ?
1
2
tan tan /
?
? =
2
?
=
1
tan
2
?
x
x = sin ?
v =
1
2sin cos
tan
cos2
?
? ? ? ?
? ?
?
? ?
= 2 ?
= 2sin
-1
x
du
dv
= 2
1
2(1 x ) ?
×
2
1 x
2
?
=
3
2 2 ?
×
4
5 2 ?
=
3
10
Q.9 If
e 2
d A B C
5 7 2
cos
log | ( )|
sin cos
?
? ? ? ?
? ? ? ?
?
where C is a constant of integration, then
B
A
( ) ?
can be:
(1)
5 2 1
3
( sin )
sin
? ?
? ?
(2)
5 3
2 1
(sin )
sin
? ?
? ?
(3)
2 1
3
sin
sin
? ?
? ?
(4)
2 1
5 3
sin
(sin )
? ?
? ?
Sol. 1
2
cos
5 7sin 2 2sin
?
? ? ? ? ?
?
d ?
Put sin ? = t, cos ? d ? = dt
Page 5
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 1
Date : 5
th
September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Maths
Q.1 If x=1 is a critical point of the function f(x)=(3x
2
+ax–2–a)e
x
, then:
(1) x=1 is a local minima and
2
x
3
? ? is a local maxima of f. .
(2) x=1 is a local maxima and
2
x
3
? ? is a local minima of f. .
(3) x=1 and
2
x
3
? ? are local minima of f. .
(4) x=1 and
2
x
3
? ? are local maxima of f. .
Sol. 1
f(x) = (3x
2
+ax–2–a)e
x
f
’
(x) = (3x
2
+ax–2–a)e
x
+ (6x+a)e
x
= 0
? ?
x 2
e 3x a 6 x 2 ? ? ? ? ?
? ?
=0
at x = 1, 3 +a+6 - 2 = 0
a=–7
f(x) = (3x
2
- 7x + 5 )e
x
f
’
(x) = (6x—7)e
x
+(3x
2
-7x+5)e
x
= e
x
(3x
2
-x-2) = 0
= 3x
2
—3x + 2x - 2 = 0
= (3x+2) (x—1) = 0
x = 1, -2/3
+ – +
–2/3
1
x = 1 is point of local minima.
x = –2/3 is point of local maxima.
Q.2
? ?
2 4
1 x x 1 x
1
x 0 2 4
x e
1 x x 1
/
lim
? ? ?
?
?
? ?
? ?
? ?
? ? ?
(1) is equal to
e
(2) is equal to 1 (3) is equal to 0 (4) does not exist
Sol. 2
? ?
? ?
2 4
1 x x 1 /x
x 0 2 4
x e 1
lim
1 x x 1
? ? ?
?
? ?
?
? ?
? ?
? ? ?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 2
? ?
? ?
? ?
2
2 4
1 x x 1
x 2
2 4
2 4
x 0
x e 1 1 x x 1
lim
x x
? ?
? ? ? ? ?
? ?
? ? ?
? ?
? ?
?
? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
? ?
?
? ?
?
? ?
? ?
? ?
?
?
?
? ? ?
?
? ?
? ?
3
x x
2
3 x 0
e 1
lim 2
x x
2
2
= 1
Q.3 The statement p q p p p q ( ( )) ( ( )) ? ? ? ? ? is:
(1) equivalent to p q p ( ) (~ ) ? ?
(2) equivalent to p q p ( ) (~ ) ? ?
(3) a contradiction
(4) a tautology
Sol. 4
? ? ?
? ? ? ? ? ?
? ?
(p (q p))
p q q p p (q p) p q p p q
(p (p q))
T T T T T T T
T F T T T T T
F T F T T T T
F F T T F T T
Q.4 If
2 2
L
16 8
sin sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
and
2 2
M
16 8
cos sin
? ? ? ? ? ?
? ?
? ? ? ?
? ? ? ?
, then:
(1)
1 1
M
2 8
2 2
cos
?
? ?
(2)
1 1
M
4 8
4 2
cos
?
? ?
(3)
1 1
L
2 8
2 2
cos
?
? ? ?
(4)
1 1
L
4 8
4 2
cos
?
? ?
Sol. 1
L =
? ? ?
? ?
? ?
3
s in
1 6
sin
16
? ? ? ?
? ?
? ?
? ? ? ? ?
? ?
? ?
? ?
1
L cos cos
2 8 4
?
1
L
2 2
—
1
cos
2 8
?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 3
M =
3
cos
16
? ? ?
? ?
? ?
cos
16
? ? ?
? ?
? ?
M =
1
cos cos
2 4 8
? ? ? ?
?
? ?
? ?
M =
1
2 2
+
1
2
cos
8
?
Q.5 If the sum of the first 20 terms of the series
? ? ? ? ? ?
1 2 1 3 1 4
7 7 7
x x x
/ / /
log log log ... ? ? ? is 460,
then x is equal to:
(1) 7
1/2
(2) 7
2
(3) e
2
(4) 7
46/21
Sol. 2
(2 + 3 + 4 +... + 21)log
7
x = 460
? ?
? ?
7
20 21 2
log 460
2
? ?
? x
? ?230 log
7
x = 460 ? log
7
x = 2 ? ?x = 7
2
Q.6 There are 3 sections in a question paper and each section contains 5 questions. A
candidate has to answer a total of 5 questions, choosing at least one question from
each section. Then the number of ways, in which the candidate can choose the questions,
is:
(1) 2250 (2) 2255 (3) 1500 (4) 3000
Sol. 1
S—1 S—2 S—3
1,2,3,4,5 1,2,3,4,5 1,2,3,4,5
6 case
1
1
1
2
2
3
1
2
3
2
1
1
3
2
1
1
2
1
= 3(
5
C
1
×
5
C
2
×
5
C
2
) + 3(
5
C
1
×
5
C
1
×
5
C
3
)
= 3(5 × 5 × 2 × 5 × 2) + 3(5 × 5 × 10)
= 750 + 1500 = 2250
Q.7 If the mean and the standard deviation of the data 3,5,7,a,b are 5 and 2 respectively,
then a and b are the roots of the equation:
(1) x
2
–20x+18=0 (2) x
2
–10x+19=0 (3) 2x
2
–20x+19=0 (4) x
2
–10x+18=0
Sol. 2
S.D. =
? ?
2
2
i
x
x
n
?
?
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 4
(2)
2
=
2 2
83 a b
5
? ?
—(5)
2
4 =
2 2
83 a b
5
? ?
— 25
29×5 — 83 = a
2
+b
2
? a
2
+b
2
= 62
a b 15
5
? ?
= 5
? a b 10 ? ? ...(1)
2ab = 100 — 62 = 38
ab 19 ? ...(2)
from eq.(1) & (2)
x
2
– 10x + 19 = 0
Q.8 The derivative of
2
1
1 x 1
x
tan
?
? ?
? ?
? ?
? ?
? ?
with respect to
2
1
2
2x 1 x
1 2x
tan
?
? ?
?
? ?
? ?
?
? ?
at
1
x
2
? is:
(1)
2 3
3
(2)
2 3
5
(3)
3
12
(4)
3
10
Sol. 4
x = tan ?
u =
1
sec 1
tan
tan
?
? ? ? ?
? ?
?
? ?
= ? ?
1
2
tan tan /
?
? =
2
?
=
1
tan
2
?
x
x = sin ?
v =
1
2sin cos
tan
cos2
?
? ? ? ?
? ?
?
? ?
= 2 ?
= 2sin
-1
x
du
dv
= 2
1
2(1 x ) ?
×
2
1 x
2
?
=
3
2 2 ?
×
4
5 2 ?
=
3
10
Q.9 If
e 2
d A B C
5 7 2
cos
log | ( )|
sin cos
?
? ? ? ?
? ? ? ?
?
where C is a constant of integration, then
B
A
( ) ?
can be:
(1)
5 2 1
3
( sin )
sin
? ?
? ?
(2)
5 3
2 1
(sin )
sin
? ?
? ?
(3)
2 1
3
sin
sin
? ?
? ?
(4)
2 1
5 3
sin
(sin )
? ?
? ?
Sol. 1
2
cos
5 7sin 2 2sin
?
? ? ? ? ?
?
d ?
Put sin ? = t, cos ? d ? = dt
JEE Main 2020 Paper
5
th
September 2020 | (Shift-2), Maths Page | 5
2
dt
2t 7t 3 ? ?
?
=
1
2
2
dt
7t 3
t
2 2
? ?
?
=
1
2
2
2
dt
7 7 49 24
t t
2 4 16 16
? ?
? ? ? ?
? ?
? ?
?
=
1
2
? ? ? ?
2 2
dt
t 7 / 4 5 / 4 ? ?
?
1
2
×
1
5
2 .
4
ln
t 7 / 4 5 / 4
t 7 / 4 5 / 4
? ? ? ?
? ?
? ?
? ?
1
5
ln
sin 1 / 2
sin 3
? ? ? ?
? ?
? ?
? ?
+C
B
A
( ) ?
=
2sin 1
5
sin 3
? ? ? ?
? ?
? ?
? ?
Q.10 If the length of the chord of the circle, x
2
+y
2
= r
2
(r>0) along the line, y–2x=3 is r, then
r
2
is equal to:
(1) 12 (2)
24
5
(3)
9
5
(4)
12
5
Sol. 4
3
5
r
(0,0)
M
A
B
AB =
2
2 r 9 / 5 ?
=r
r
2
—9/5 =
2
r
4
3r
2
/4 = 9/5
2
12
r
5
?
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