关于三角函数的题目sin^21+sin^22+sin^23+.sin^290=?帮忙解下谢谢要详细步骤给我讲明白啊谢啦.

Question

关于三角函数的题目
sin^2 1 + sin^2 2 + sin^2 3 + .sin^2 90 =?
帮忙解下谢谢 要详细步骤 给我讲明白啊谢啦.

Answer 1

sin^2 1=cos^2 89
sin^2 2=cos^2 88
sin^2 x=cos^2 (90-x)
sin^2 45=0.5
所以sin^2 1 + sin^2 2 + sin^2 3 + .sin^2 90=44+0.5+1=45.5