Question

Pentru ctg x= 3, calculati cos^2 x.

Answer 1

ctg x= cosx/sinx=3=> 3sinx=cosx
=>9sin^2 x=cos^2x
sin^2 x+ cos^2 x=1
sin^2 x=1-cos^2 x

9(1-cos^2 x)=cos^2 x
9-9cos^2 x=cos^2 x
10cos^2 x=9
cos^x=9/10

asa cred ca e