Question

Нужна помощь
Верно ли равенство:
1) sin 7pi/12 - sin pi/12 = корень 2 / 2
2) cos 11pi/24 - cos pi/8 = -sin 7pi/24
3) sin 11pi/18 + sin 7pi/18=cos 2pi/9
4) cos 5pi/8+cos pi/8=корень 2 *cos 3pi/8

Answer 1

1)sin7π/12-sinπ/12=√2/2
sinπ/12-sinπ/12=√2/2-неверно
2)cos11π/24-cosπ/8=-sin7π/24
-2sin(11π/24+π/8)/2*sin(11π/24+π/8)/1=-2sin14π/48*sin8π/48=-2sin7π/24*sinπ/6=
=-2*1/2*sin7π/24 -верно
3)sin11π/18+sin7π/18=cos2π/9
sin11π/18+sin7π/18=2sin(11π/18+7π/18)/2*cos(11π/18-7π/18)/2=
=2sinπ*cos4π/18=j -неверно
4)cos5π/8+cosπ/8=√2*cos3π/8
cos5π/8+cosπ/8=2cos(5π/8+π/8)*cos(5π/8-π/8)=2cos3π/4*cosπ/2=0 -неверно