Question: what is sin x arctan?
Answer: Draw a triangle in the plane with vertices (1,x) , (1,0) , and the origin. Then arctan(x) is the angle between the positive x-axis and the ray beginning at the origin and passing through (1,x) . Therefore, sin(arctan(x)) sin ( arctan ( x ) ) is x√12+x2 x 1 2 + x 2 . One to any power is one.