Question

Найти 4cos2x, если sinx=-0,5

Answer 1

$4cox2x=4(cos^{2}x-sin^{2}x)=4(1-sin^{2}x-sin^{2}x)=4-8*sin^{2}x=$$4-8*0.25=2$

Answer 2

4cosx2x=

4(cos^x-sin^2x)=

4(1-sin^2x-sin^2x)=

4(1-2sin^2x)=

4-8sin^2x=

4-8*(-0,5)^2=

4-8*0,25 =2