已知sina和cosa是方程X^2-MX+M-1=0的两和实数根,且0'

问题描述:

已知sina和cosa是方程X^2-MX+M-1=0的两和实数根,且0'

sin²a + cos²a = 1
(sina + cosa)² - 2sinacosa = 1
m² - 2(m-1) = 1
m = 1
x1 = 0,x2 = 1
则a=90°