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If the eccentricity of the hyperbola x– y2 sec2 a = 5 is times the eccentricity of the ellipse x2 sec2 a + y2 = 25, then a value e of a is
a) π/6 
b) π/4
c) π/3 
d) π/2
Correct answer is option 'B'. Can you explain this answer?
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If the eccentricity of the hyperbola x2–y2sec2a = 5 is times the eccen...
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If the eccentricity of the hyperbola x2–y2sec2a = 5 is times the eccen...
To find the value of 'a' that satisfies the given condition, we need to compare the eccentricities of the hyperbola and the ellipse.

1. Equation of the hyperbola: x^2 - y^2sec^2(a) = 5
2. Equation of the ellipse: x^2sec^2(a) + y^2 = 25

Let's find the eccentricities of both the hyperbola and the ellipse.

Eccentricity of the hyperbola:
The eccentricity of a hyperbola is given by the formula e = √(1 + b^2/a^2), where a and b are the semi-major and semi-minor axes, respectively.

From the equation of the hyperbola, we can observe that a = √5 and b = √(5sec^2(a)). Substituting these values into the eccentricity formula, we get:
e_h = √(1 + (5sec^2(a))/(5)) = √(1 + sec^2(a)) = √(1 + 1/cos^2(a))

Eccentricity of the ellipse:
The eccentricity of an ellipse is given by the formula e = √(1 - b^2/a^2), where a and b are the semi-major and semi-minor axes, respectively.

From the equation of the ellipse, we can observe that a = √25 = 5 and b = √(25sec^2(a)) = 5sec(a). Substituting these values into the eccentricity formula, we get:
e_e = √(1 - (25sec^2(a))/(25)) = √(1 - sec^2(a)) = √(1 - 1/cos^2(a))

Now, we are given that the eccentricity of the hyperbola is times the eccentricity of the ellipse. Mathematically, this can be written as:
e_h = k * e_e

Substituting the expressions for e_h and e_e derived earlier, we have:
√(1 + 1/cos^2(a)) = k * √(1 - 1/cos^2(a))

Squaring both sides of the equation, we get:
1 + 1/cos^2(a) = k^2 * (1 - 1/cos^2(a))

Simplifying the equation, we have:
1 = k^2 - k^2/cos^2(a)
1 = k^2(1 - 1/cos^2(a))

Since cos^2(a) can never be negative, we can divide both sides of the equation by (1 - 1/cos^2(a)), which gives:
1/(1 - 1/cos^2(a)) = k^2

Simplifying further, we get:
cos^2(a)/(cos^2(a) - 1) = k^2

Using the identity cos^2(a) - sin^2(a) = 1, we can rewrite the equation as:
cos^2(a)/(sin^2(a)) = k^2
cot^2(a) = k^2

Taking the square root of both sides, we get:
cot(a) = k

We know that cot(a) = 1/tan(a). Sub
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If the eccentricity of the hyperbola x2–y2sec2a = 5 is times the eccentricity of the ellipse x2sec2a + y2= 25, then a value e of a isa)π/6b)π/4c)π/3d)π/2Correct answer is option 'B'. Can you explain this answer?
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