已知向量a=(cos1.5x,sin1.5x),b=(cos0.5x,-sin0.5x)且x在0—90度之间求a+b向量的模a+b=(cos1.5x+cos0.5x,sin1.5x-sin0.5x),所以la+bl^2=(cos1.5x+cos0.5x)^2+(sin1.5x-sin0.5x)^2=2+2cos2x=2-2[(sinx)^2-(cosx)^2]=2-2[(sinx)^2+(cosx)^2]+4(cosx)^2=

Answer 1

1.（cos1.5x+cos0.5x)^2+(sin1.5x-sin0.5x)^2=(cos1.5x)^2+2cos1.5xcos0.5x+(cos0.5x)^2+(sin1.5x)^2-2sin1.5xsin0.5x+(sin0.5x)^2(cos1.5x)^2+(sin1.5x)^2=1 (cos0.5x)^2+(sin0.5x)^2=12cos1.5xcos0.5x-2sin1.5xsin...