Q8 of 268 Page 5

If, sin 50° = α then write the value of cos 50° in terms of α.

We know that

cos² θ + sin² θ = 1

⇒ cos² 50° + sin² 50° = 1

⇒ cos ² 50° = 1 – sin² 50°

⇒ cos 50° = √(1 – sin² 50°)

And Given that sin 50° = a

⇒ cos 50° = √(1 – a² )

If sin 77° = x, then write the value of cos 77^o in terms of x.

If cos55° = x², then write the value of sin 55^o in terms of x.

If x cos A = 1 and tan A = y, then what is the value of x² – y².

Prove the followings identities:

(1 – sin θ)(1 + sin θ) = cso² θ