Question

If tan-1(x2 +y2) = α then dy/dx is equal to

(1) xy

(2) - xy

(3) -x/y

(4) x/y

Answer 1

Correct option (3) -x/y

Explanation:

tan-1 (x2 +y2) = α

⇒ x2 + y2 = tan α

Differentiating w.r.t. x, we get 2x +2y dy/dx = 0

⇒ dy/dx = -x/y.