Question

If `theta` is an acute angle and `sintheta=1/2`, then what is `costheta`?

Answer 1

`sqrt3/3`

Explanation:

Use trig identity:
`cos^2 a + sin^2 a = 1`
`cos^2 t = 1 - sin^2 t = 1 - 1/4 = 3/4`
`cos t = +- 1/sqrt3 = +- sqrt3/3`
Since t is an acute angle, then cos t is positive.
`cos t = sqrt3/3`