Explanation:

Sin^-1 3/  5 + tan^-1 1 / 7

Let A=sin^-1 3 / 5 or sin A = 3/5 ⇒ cos A = 4/5

tan B = 3/4

And B = tan^-1 1 / 7 or tan B = 1/7

Now A + B = tan^-1 (tan A) + tan^-1 (tan B) = tan^-1 3 / 4 + tan^-1 1 / 7

= tan^-1 ( 3 / 4 + 1 / 7 x 1 − 3 / 28) = tan^-1 1 = π/4