题目3单选题
已知α是第二象限角,sinα=<img src="https://p.ananas.chaoxing.com/star3/origin/363ea78cf2cf88f85eaa90c4d61aa085.png">,则cosα等于A. <img src="https://p.ananas.chaoxing.com/star3/origin/b0feafd10e9ccf79e59fc4213674bb07.png">B. <img src="https://p.ananas.chaoxing.com/star3/origin/640db80d1ba4a1c50098e0b146ca8c07.png">C. <img src="https://p.ananas.chaoxing.com/star3/origin/363ea78cf2cf88f85eaa90c4d61aa085.png">D. <img src="https://p.ananas.chaoxing.com/star3/origin/3abfe68020fd009fe8434a7c043bb098.png">