Question

prove that sin 20 + sin 40 + cos 190 is equals to zero​

Answer 1

Answer:

sin 20+sin40-sin80

2sin30 cos10 -sin(90-10)

2(1/2)cos10-cos10

cos10- cos10=0

Answer 2

$\sf \sin(20) + \sin(40) + \sin(80)$

2sin30 cos10 -sin(90-10)

$\sf 2 \frac{1}{2}cos10-cos10$

cos10 - cos 10 = 0