Question

Se da:
$cos \alpha = - 0.6 \\ \frac{\pi}{2} < \alpha < \pi \\ de \: aflat \: \\ sin \alpha \\ tg \alpha \\ ctg \alpha$

Answer 1

cos α=-0,6=-6/10=-3/5
sin²α+cos²α=1
sin²α=1-cos²α
sin²α=1-(-3/5)²
sin²α=1-9/25
sin²α=16/25
α∈(π/2;π) inseamna ca sinusul are valoare pozitiva.
sinα=4/5
tgα=sinα/cosα=4/5/-3/5=4/5*(-5/3)=-5*4/3*5=-4/3
ctgα=1/tgα=1/-4/3=-3/4