Thread: 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

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

(3) (i) Use the fact that:

(ii) Use the fact that: and that