# Trig

posted by
**Ashley** on
.

If cosx = 10/19 an pi < x < 2pi, find the exact value of cos x/2

Use the double angle formula.

Cos 2Y= sin^2 Y - cos^2Y = 1-2Cos^2 Y.

let y= x/2, and 2Y=x

posted by
**Ashley** on
.

If cosx = 10/19 an pi < x < 2pi, find the exact value of cos x/2

Use the double angle formula.

Cos 2Y= sin^2 Y - cos^2Y = 1-2Cos^2 Y.

let y= x/2, and 2Y=x