Question

evaluate:cos70/sin20+cos59/sin31-8sin^230

Answer 1

$\cos(70) = \cos(90 - 20 ) = \sin(20) \\ \cos(59) = \cos(90 - 31) = \sin(31) \\ 8 \times ( \sin {}^{2} (30) = )( \frac{1}{2} ) ^{2} = \frac{8}{4} = 2 \\ 1 + 1 - 2 = 0$