Question

Sin780Sin480+Cos240Cos300=1/2

Answer 1

Answer:

Sin780° = Sin(360 + 360 + 60)° = Sin60° = √3/2.

Sin480° = Sin(360 + 90 + 30)° = Cos30° = √3/2.

Cos240° = Cos(180 + 60)° = -Cos60° = -1/2.

Cos300° = Cos(270 + 30)° = Sin30° = 1/2.

So, Sin780° × Sin480° + Cos240° × Cos300°

= (√3)²/(2)² + (-1)(1)/(2)².

= (3/4) - (1/4).

= (3 - 1)/4.

= 2/4.

= 1/2.

Hence Proved.

Hope this helps!!

Answer 2

Hope it's help you....☝️♥️