如果α∈(π/2,π),且sinα=4/5,那么sin(α+π/4)+cos(α+π/4)=A.(4根号2)/5B.-(4根号2)/5C.(3根号2)/5D.-(3根号2)/5
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![如果α∈(π/2,π),且sinα=4/5,那么sin(α+π/4)+cos(α+π/4)=A.(4根号2)/5B.-(4根号2)/5C.(3根号2)/5D.-(3根号2)/5](/uploads/image/z/6901068-12-8.jpg?t=%E5%A6%82%E6%9E%9C%CE%B1%E2%88%88%28%CF%80%2F2%2C%CF%80%29%2C%E4%B8%94sin%CE%B1%3D4%2F5%2C%E9%82%A3%E4%B9%88sin%28%CE%B1%2B%CF%80%2F4%29%2Bcos%28%CE%B1%2B%CF%80%2F4%29%3DA.%284%E6%A0%B9%E5%8F%B72%29%2F5B.-%284%E6%A0%B9%E5%8F%B72%29%2F5C.%283%E6%A0%B9%E5%8F%B72%29%2F5D.-%283%E6%A0%B9%E5%8F%B72%29%2F5)
如果α∈(π/2,π),且sinα=4/5,那么sin(α+π/4)+cos(α+π/4)=A.(4根号2)/5B.-(4根号2)/5C.(3根号2)/5D.-(3根号2)/5
如果α∈(π/2,π),且sinα=4/5,那么sin(α+π/4)+cos(α+π/4)=
A.(4根号2)/5
B.-(4根号2)/5
C.(3根号2)/5
D.-(3根号2)/5
如果α∈(π/2,π),且sinα=4/5,那么sin(α+π/4)+cos(α+π/4)=A.(4根号2)/5B.-(4根号2)/5C.(3根号2)/5D.-(3根号2)/5
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