第八题 已知
来源:学生作业帮 编辑:搜搜考试网作业帮 分类:数学作业 时间:2024/07/10 08:26:37
![](http://img.wesiedu.com/upload/8/e6/8e629759d1d4ee11c87f993ab71e2bf9.jpg)
![第八题 已知](/uploads/image/z/20075476-4-6.jpg?t=%E7%AC%AC%E5%85%AB%E9%A2%98+%E5%B7%B2%E7%9F%A5)
解题思路: 三角函数公式的应用 ,
解题过程:
解 (1)(4sina-2cosa)/(5cosa+3sina)= (4tana - 2)/(5 + 3tana) = (12 - 2)/(5 + 9)= 10/14= 5/7,(分子分母同时除以 tana)
(2) sinacosa = sinacosa /(sin2a + cos2)= tana / (tan2a + 1)= 3/ 10;
(3) (sina + cosa)2 = sin2a + 2sinacosa + cos2a = 1 + 2sinacosa = 1 + 3/5 = 8/5
解题过程:
解 (1)(4sina-2cosa)/(5cosa+3sina)= (4tana - 2)/(5 + 3tana) = (12 - 2)/(5 + 9)= 10/14= 5/7,(分子分母同时除以 tana)
(2) sinacosa = sinacosa /(sin2a + cos2)= tana / (tan2a + 1)= 3/ 10;
(3) (sina + cosa)2 = sin2a + 2sinacosa + cos2a = 1 + 2sinacosa = 1 + 3/5 = 8/5