Question

упростите выражение: 2cos^2 альфа/2-cosальфа-1

Answer 1

$2Cos^{2}\frac{a}{2} - Cosa - 1 = 2Cos^{2}\frac{a}{2} - Cos2\frac{a}{2} - 1 =$

$2Cos^{2}\frac{a}{2} - (Cos^{2}\frac{a}{2} - Sin^{2}\frac{a}{2}) - 1 = 2Cos^{2}\frac{a}{2} - Cos^{2}\frac{a}{2} + Sin^{2}\frac{a}{2} - 1 =$

$Cos^{2}\frac{a}{2} + Sin^{2}\frac{a}{2} - 1 = 1 - 1 = 0$