Question

Помогите, пожалуйста с 15, 16 и 17 заданиями :\

Answer 1

$15) sin \frac{ \pi }{16} cos \frac{3 \pi }{16} +cos \frac{ \pi }{16} sin \frac{3 \pi }{16} =sin( \frac{ \pi }{16} + \frac{3 \pi }{16} )=sin \frac{4 \pi }{16} =sin \frac{ \pi }{4} = \\ = \frac{ \sqrt{2} }{2}$

$16) cos ^{2} 5 ^{0} -sin5 ^{0} =cos2*5 x^{2} =cos10 ^{0}$

$17) \frac{sina}{1-cosa} + \frac{1-cosa}{sina} = \frac{sina*sina}{sina(1-cosa)} + \frac{(1-cosa)(1-cosa)}{sina(1-cosa)} = \\ = \frac{sin^{2} a}{sina(1-cosa)} + \frac{1-cos^{2} a}{sina(1-cosa)} = \frac{sin ^{2} a+sin ^{2} a}{sina(1-cosa)} = \frac{2sin ^{2} a}{sina(1-cosa)} = \\ = \frac{2sina}{1-cosa}$