Question

4 sin^2 x - 3 , если cos X =0,2 ​

Answer 1

$4\sin^2x-3=4(1-\cos^2x)-3=4-4\cos^2x-3=\\=1-4\cos^2x=1-4\cdot0.2^2=1-4\cdot0.04=1-0.16=0.84$