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#6cfd5662-f083-46a8-b5b3-05f8c9d4b371基础填空题两角和与差的公式三角函数与三角恒等变换

1. (2023春•台江区校级期末)已知α\alphaβ\beta都是锐角,sinα=35,cos(α+β)=513\sin \alpha =\frac{3}{5},\cos (\alpha +\beta )=-\frac{5}{13},则cosβ=(\cos \beta =(  ))