Question

tana=-4/3求2(sina)^2+sinacosa-3(cosa)^2

Answer 1

2(sina)^2+sinacosa-3(cosa)^2

(2(sina)^2+sinacosa-3(cosa)^2)/1

=(2(sina)^2+sinacosa-3(cosa)^2)/((sina)^2+(cosa)^2)

分子分母都除以(cosa)^2

=(2(tana)^2+tana-3)/((tana)^2+1)

tana=-4/3代入得

=-7/25