Question

Find cos Θ/2 when 270º<Θ<360º and cosΘ is defined as indicated.
cos Θ =√7/4

Answer 1

\[\cos(\frac{\theta}{2})=\pm\sqrt{\frac{1+\cos(\theta)}{2}}\]

Answer 2

\[\cos(\frac{\theta}{2})=\pm\sqrt{\frac{1+\frac{\sqrt7}{4}}{2}}\]

Answer 3

use the \(-\) not the \(+\) because half an angle in quadrant 4 is in quadrant 2, and in quadrant 2 cosine is negative

Answer 4

is it \[-\sqrt{4-\sqrt{7}}/4+\sqrt{7}\]

Answer 5

@misty1212