已知tanα=2,求 3sin²α+3sinαcosα-2cos²α
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/04 12:55:43
![已知tanα=2,求 3sin²α+3sinαcosα-2cos²α](/uploads/image/z/1816043-59-3.jpg?t=%E5%B7%B2%E7%9F%A5tan%CE%B1%3D2%2C%E6%B1%82+3sin%26%23178%3B%CE%B1%2B3sin%CE%B1cos%CE%B1-2cos%26%23178%3B%CE%B1)
已知tanα=2,求 3sin²α+3sinαcosα-2cos²α
已知tanα=2,求 3sin²α+3sinαcosα-2cos²α
已知tanα=2,求 3sin²α+3sinαcosα-2cos²α
3(sinα)^2+3sinαcosα-2(cosα)^2
=[3(sinα)^2+3sinαcosα-2(cosα)^2]/[(sinα)^2+(cosα)^2] 分子分母同除(cosα)^2
=[3(tanα)^2+3tanα-2]/[(tanα)^2+!]
=(3*4+3*2-2)/(4+1)
=16/5
16/5
见图