—Are you free this Sunday? — Yes. If it_____ , I will go shopping with mum. A. won’t rain B. isn’t raining C. doesn’t rain D. didn’t rain 答案:C12.已知A,B,C三点的坐标分别是A(3,0),B(0,3),C(sinα,cosα),其中90°<α<270°.(1)若|$\overrightarrow{AC}$|=|$\overrightarrow{BC}$|,求角α的值;(2)$\overrightarrow{AC}$•$\overrightarrow{BC}$=-1,求$\frac{si{n}^{2}α+sinαcosα}{1+tanα}$的值.