Question

Prove that sin square 20 degree + sin square 70 degree minus 10 square 45 degree is equal to zero

Answer 1

sin(sq) 20 + sin(sq) 70 - tan(sq) 45

= sin(sq)20 + sin(sq) [90 - 20] - (1) sq [tan 45 = 1]

= sin(sq)20 + cos(sq) 20 - 1 [sin(sq)[90 - A] = cos(sq)A]

= 1 - 1 [Identity: sin(sq)A + cos(sq)A = 1]

= 0

so the ans is 0