(d) If \( P(A) = \frac{3{13} \), \( P(B) = \frac{5}{13} \), and \( P(A \cap B) = \frac{2}{13} \), find the value of \( P(B/A) \):
If \[ y = 500 e^{7x} + 600 e^{-7x}, \quad \text{then show that} \quad \frac{d^2 y}{dx^2} = 49y. \]
Find the area of the region enclosed by the ellipse \[ \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1. \]
Find the value of \[ \int \frac{\sec^2 2x}{(\cot x - \tan x)^2} \, dx. \]
Prove that \[ \int_0^{\pi} \frac{x \tan x}{\sec x + \tan x} \, dx = \frac{\pi}{2} (\pi - 2). \]
Prove that the height of the cylinder of maximum volume inscribed in a sphere of radius \( R \) is \( \frac{2R}{\sqrt{3}} \).
Solve the differential equation \[ (x + y) \, dy + (x - y) \, dx = 0, \quad \text{if} \quad y = 1 \text{ when } x = 1. \]