Question

Prove that sin 120° cos 330° + cos 240° sin 330º = 1​

Answer 1

Answer:

Sin(180–60)*cos(90+60) - cos(270–30)*sin(360–30)

= Sin60* (-Sin60)- (-sin30)*(-sin30)=-3/4–1/4 = -4/4 = -1

You made a mistake at step 2

Cos(90+60)= - Sin 60 not Sin 60.

Step-by-step explanation:

Answer 2

Step-by-step explanation:

Taking LHS:

sin 120° × cos 330° + cos 240° × sin 330°

sin (90+30)° × cos (360-30)° + cos (270-30)° × sin (360-30)°

cos 30° × cos 30° + (- sin 30°)(- sin 30°)

cos² 30° + sin² 30°

1

Therefore LHS=RHS

Hence proved.