Question

2-3sin patrat alfa daca se stie ca cos alfa =-0,3

Answer 1

$sin^{2} a+ cos^{2} a=1 \\ sin^{2} a=1- cos^{2} a\\sin^{2}a=1-(-0,3)^{2}=1-0,09=0,91= \frac{91}{100} \\2- sin^{2} a=2-0,91=1,09= \frac{109}{100}$