Question

Prove that sin ( -690^°) cos (-300^°) + cos (-750^°) sin (-240^°) = 1

Answer 1

Answer:

sin 600 . cos 330 + cos 120 . sin 150 = 1

sin (1 × 360 + 240) . cos (360 - 30) + cos (180 - 60) . sin (180 - 30) = 1

sin 240 . cos 30 + (-cos 60) . sin 30 = 1

sin (180 + 60) . 1/2√3 - 1/2 . 1/2 = 1

-sin 60 . 1/2√3 - 1/4 = 1

-1/2√3 . 1/2√3 - 1/4 = 1

-3/4 - 1/4 = 1

-4/4 = 1

-1 ≠ 1

Step-by-step explanation: