若tan&=2,则cos2&分之1+sin2&=(有过程)
问题描述:
若tan&=2,则cos2&分之1+sin2&=(有过程)
答
若tan&=2,则cos2&分之1+sin2&=?cos2&=cos²&-sin²& ,sin2&=2sin&cos&tan&=2sin&=2cos& ,1=cos²&+sin²& cos2&/1+sin2&=(cos²&-sin²&)/(1+2sin&cos&)=(cos²&-4cos²&)/(cos&sup...