cosa=1/17 cos(a+b)=-47/51 a>0 b

问题描述:

cosa=1/17 cos(a+b)=-47/51 a>0 b

其他人气:192 ℃时间:2020-06-02 23:27:07
优质解答
cosb
=cos(a+b-a)
=cos(a+b)cosa+sin(a+b)sina
=-47/51*1/17+14√2/51*12√2/17
=1/3
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cosb
=cos(a+b-a)
=cos(a+b)cosa+sin(a+b)sina
=-47/51*1/17+14√2/51*12√2/17
=1/3