# Math Help - identities

1. ## identities

1.Show that the following is true: (sin 30°)2 + (cos 30°)2 = 1

2.
For 120°, show that tan T = sin T/cos T

3.Prove the following identities:
• cotT sinT = cosT
• sin2T sec2T = sec2T - 1

2. (1) & (2) : What are you have troubles with? Simply calculate them.

(3) (i) Use the fact that: $\cot x = \frac{\cos x}{\sin x}$

(ii) Use the fact that: $\sec^2 x = \frac{1}{\cos^2 x}$ and that $\tan^2 x = \sec^2 x - 1$