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cos(a+30)=0.6 (0,90) 求cosa
人气:127 ℃ 时间:2020-05-30 05:57:02
解答
cos(a+30)=0.6 ->sin(a+30)=0.8
->cosa=cos(a+30-30)=cos(a+30)cos30+sin(a+30)sin30=0.6*0.866+0.8*0.5
=0.9196
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