Question

Найдите cos a, tg a, если sin
a = 2/5

Answer 1

По основному тригонометрическому тождеству cos$alpha$=$sqrt{1-sin^{2} alpha}$=$sqrt{1-frac{4}{25}}$=$frac{sqrt{21}}{5}$

tg$alpha$=$frac{sinalpha}{cosalpha}$=$frac{frac{2}{5}}{frac{sqrt{21}}{5}}$=$frac{2}{sqrt{21}}$=$frac{2sqrt{21}}{21}$