Объяснение:
1.
в) tgC=AB/AC
2.
5tg45-3cos60=5×1-3×1/2=5-3/2=3,5
3.
<C=90
sinB=0,4
AC=8 cм
АВ=?
sinB=AC/AB
AB=AC/sinB
AB=8 :0,4=20 cм
4.
sina^2+cosa^2=1
cosa^2=1-sina^2
Cosa^2=1-(4/5)^2=1-16/25=9/25
cosa=3/5
tga=sina/cosa=4/5:3/5=4/5×5/3=4/3=1 1/3
ctga=cosa/sina=3/5:4/5=3/5×5/4=3/4
