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来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/07/04 17:32:48
![](http://img.wesiedu.com/upload/9/a5/9a5f10fa4f0f76979a54abafdcaff74a.jpg)
解题思路: 考查同角三角函数的基本关系,和角差角公式
解题过程:
在Word里,没法打角斯塔,用a表示,见谅!
解:cos2(a+15。)+sin2(a-15.)+sin(a+180。)cos(a-180。)
=cos2(a+15。)+sin2(a+15。)-sin2(a+15。)+sin2(a-15。)+sinacosa =【cos2(a+15。)+sin2(a+15。)】+【sin2(a-15。)-sin2(a+15。)】+sinacosa =1+[sin2(a-15。)-sin2(a+15。)]+sinacosa
=1+[sin(a-15。)+sin(a+15。)][sin(a-15。)-sin(a+15。)]+sinacosa
=1+[2sinacos15。]*(-2cosa*sin15。)+sinacosa =1-[2sinacosa]*(2sin15。cos15。)+sinacosa
=1-sin2a*sin30。+(1/2)*sin2a
=1-(1/2)*sin2a+(1/2)*sin2a
=1
最终答案:1
解题过程:
在Word里,没法打角斯塔,用a表示,见谅!
解:cos2(a+15。)+sin2(a-15.)+sin(a+180。)cos(a-180。)
=cos2(a+15。)+sin2(a+15。)-sin2(a+15。)+sin2(a-15。)+sinacosa =【cos2(a+15。)+sin2(a+15。)】+【sin2(a-15。)-sin2(a+15。)】+sinacosa =1+[sin2(a-15。)-sin2(a+15。)]+sinacosa
=1+[sin(a-15。)+sin(a+15。)][sin(a-15。)-sin(a+15。)]+sinacosa
=1+[2sinacos15。]*(-2cosa*sin15。)+sinacosa =1-[2sinacosa]*(2sin15。cos15。)+sinacosa
=1-sin2a*sin30。+(1/2)*sin2a
=1-(1/2)*sin2a+(1/2)*sin2a
=1
最终答案:1