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