Question

Приведите выражение к тригонометрической функции угла из промежутка [0; p/2]

Cos 0,7p;

sin 1,6p;

ctg (-3p/7);

tg (-9p/5 ).

Answer 1

a) $cos 0.7pi=cos (0.5pi+0.2pi)=-sin0.2pi$

или $cos 0.7pi=cos(pi-0.3pi)=-cos0.3pi$

б) $sin1.6pi=sin(2pi-0.4pi)=-sin0.4pi$

в) ${rm ctg}bigg(-dfrac{3pi}{7}bigg)=-{rm ctg}bigg(pi-dfrac{4pi}{7}bigg)={rm ctg}dfrac{4pi}{7}$

г) ${rm tg}bigg(-dfrac{9pi}{5}bigg)=-{rm tg}bigg(pi+dfrac{4pi}{5}bigg)=-{rm tg}dfrac{4pi}{5}$