Basic Concepts, Why Trigonometry - Trigonometric Functions Video Lecture - Class 11

hello friends this video on trigonometry
part 1 is brought you by exam fear calm
no more fear from exam in this video we
will study techno metric functions in
techno metric functions will study
techno metric concepts degree measures
and Radian measures sine cos and tan
introduction graphs of sine cos and tan
trigonometric functions principle and
general solutions now the first question
before we study agreement why do we need
trigonometry
let me take some example let's suppose
you are standing here in this tower and
is the ocean one enemy is coming in the
ship you want to find out how far is it
enemy because you want to protect
yourself in such case we can use
trigonometric function because you know
the height of this tower you must be
knowing that since you are in the tower
and through by not cooler if you can
find the angle the angle between the
tower and the ship you can find this
distance using tonometry techno mentor
you can trick no matter you can have
this formula of tan theta this is equal
to D by H so if we have this theta no
this value of this you know the value of
H so you get the value of D also if you
want to find the speed the speed with
which this ship is coming we can use
same techni metric concept find the
speed so those we know that we do have
practical application of Timna metal in
our real life also we can have a for
example let's suppose this you again
standing behind tree and someone is
trying to approach you in the car you
want to know how far is the car from you
you want know this distance you can
easily know if you know the height of
this place
you know because you are in this you
stay in this area you know pretty well
the height of this small mountain and
then if you know the angle if you can
see the car you can find the angle just
by looking at the car and you know the
height of this my own you can very well
get the D here also we can apply the
same formula tan theta is going to H by
D since we know theta we know the value
of this and since we know we know the
value of H that is known to us so we can
find the value of B here so if you want
to know the speed if you want to find
the speed of the car we can very well do
that to do that what we have to do we
can measure the value of theta in two
different time theta one and let's
suppose after some time this theta this
is theta 1 so here in this case we have
to find theta 1 and theta 2 that is the
angle that car substance at a given
point of time at two different point t1
and t2 for example this is the car was
here at t1 the car was here at T 2 so we
can find these two angles and then we
can find the distance d1 and d2 for
example in one case will get d1 in one
case will get D 2 and then we get the
difference D 1 D 2 and we know the time
so we can find the speed this may look
complex to you but just we should know
that using trigonometry we can find such
things in our real life if you want to
find a distance of our distant object
when we know some parameter and we know
the angle theta we can find that also if
you want to find the speed of the object
coming approaching to us we can do that
if you have not understood this part
don't worry we'll do this thing integral
metric and you concept will be clear
just just to know that we can do things
that if you material introduce you this
concept Oh what is trigonometry
trigonometry if you break the word this
trigonal glass metal trigger no means
triangle and mate remains measurement
that is it is nothing but measurement of
triangle now what is triangle triangle
is if you break the word is try try to
us angle try plus engine time is 3 so
anything which has three sides is called
triangle so if you take if we have three
side this is a triangle this is a
triangle it has 3 side
this is also a triangle anything which
has three sides is a triangle but its
angle it's a good cushion angle is
rotation of a line about the fixed point
example we have this line a V and let's
suppose we take this point be fixed we
rotate this point B here so here what we
get is B dash so this is nothing but
angle angle is nothing but measure of
rotation of a line about the fixed point
so here we have wrote it rotated V dash
to this much so we can make me call it
theorize so we let's suppose we rotate
this be further to get this point so
this is called I will call V Double Dash
so this point will be theta and ever
time so what is angle angle is nothing
but rotation of the line about the fixed
point now we'll take some concepts in
angles parts of angle one is initial
side terminal side and the British these
are three parts of our angle initial
side is the side from which we start
terminal side in the side where you end
and what takes is the point from the
irritated for example the last slide we
have seen this a B was the line so this
is the initial side now about the point
a we have rotated V to this point that
is V dash so this is called terminal
side this is called initial side and
this point is called vertex that will be
once again initial side is the side from
where you start terminal side is the
side where you end and the vertex is the
point about which you rotate so this is
the angle see down they are two types of
angles one is positive and the other is
negative so what so when we rotate this
angle in the anti-clockwise direction it
is positive example if this is a line a
B and if you rotate this too
this side in the anti-clockwise
direction this is positive angle
similarly for line a B if you rotate
this line in the clockwise direction B -
so this becomes negative angle here if
you see this is the initial side this is
the terminal side so you have rotated
from here to here this is called oath
eita positive this is the initial side
we have rotated this line in clockwise
direction it becames or theta negative
major of our angle is nothing but the
amount of rotation per form we already
discussed measure of angle is nothing
but the amount of rotation perform
example if this is the line we rotate it
this much discuss the line EB we rotate
this about point a this much so this
becomes again B - so this is Theta theta
is nothing but the amount of rotation
perform from initial side to get the
terminal side this is what measure of
angle and there are two types of measure
of angle one is the degree measure and
the other is the Radian measure we
discuss it in the next slide thank you
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