Cos^2 x - sin^2 x если cosx=0.25 cos^2 x, если tanx=12

Question

Cos^2 x - sin^2 x если cosx=0.25

cos^2 x, если tanx=12

Answer 1

Sin^2=1-cos^2

cos^2x-sin^2x=2cos^2x-1=2*0.0625-1=-0.875

cos^2+sin^2=1

tg^2+1=1/cos^2
cos^2=1/(tg^2+1)

cos^2x=1/(tg^2x+1)=1/(144+1)=1/145