If sin⁡ x=−5/13, and 270°<x<360°, find cos⁡(x/2).

Answer 1

Its quadrant 3, so opposite x=-5 and hypotenuse is 13...

pythagorean says adjacent is -12

cosine is -12/13

Answer 2

Sin(x) = -5/13 is in the 4th quadrant, and x= -22.62°

Then Cos(-22.62/2) = Cos(-11.31°) = 0.98