Question

What is `cos(arc sin (5/13))`?

Answer 1

12/13

Explanation:

Call x the arc (angle) whose sin is `(5/13)`
sin x = 5/13, find cos x.
`co^2 x = 1 - sin^2 x = 1 - 25/169 = 144/169`
`cos x = +- 12/13`
Since x is in Quadrant 1 (`sin x = 5/13`), then, cos x is positive.
`cos x = 12/13`