Help with Double Angle Identities

[whittwhitt]

Help with Double Angle Identities!

cos θ = 24/25

The angle lies in quadrant 1; 0<θ<90

Find sin2θ



I know you would use either the formula cos^2θ - sin^2θ or 2sinθcosθ
And I know that the answer is 339/625, but I do not know how to get that answer?

 

[Simon Bridge]

Use trig formulae and Pythagoras.
It helps if you sketch the angle in a rt-angled triangle.

 

[lurflurf]

hint: first find sin θ