Question

Evaluate cosθ when sinθ = -7/8 and θ is in Quadrant IV.

Answer 1

cosθ=
`( √(15) )/(8)`

Explanation:

Please see attached picture for full solution.

In the 4th quadrant, the cosine of an angle is positive.

The opposite side takes the negative sign in -⅞ since it is below the x-axis. Likewise, we reject
`x = - √(15)` since x lies on the right side of the y axis.