早教吧
育儿知识
作业答案
考试题库
百科
知识分享
早教吧作业答案频道
-->数学-->
llllllllllllllllllllllllllllllllllllllllllllllllll(514:31:4)已知sin(π-a)-cos(π+a)=√2/3,且0<a<π,求sin(kπ+a)-cos(kπ+α)(k是整数)的值
题目详情
▼优质解答
答案和解析
sin(π-a)-cos(π+a)=√2/3
由诱导公式,sina+cosa=√2/3<1,可知,π/2
则√2sin(a+π/4)=√2/3
√2sin(a-π/4)=-√2cos(a+π/4)=√2√(1-sin^2(a+π/4))=4/3
即,sina-cosa=4/3
故,当k为偶数时,sin(kπ+a)-cos(kπ+α)=sina-cosa=4/3
当k为奇数时,sin(kπ+a)-cos(kπ+α)=cosa-sina=-4/3
若综合上述,还可表示成sin(kπ+a)-cos(kπ+α)=(-1)^k*4/3
看了
llllllllllllll...
的网友还看了以下:
相关搜索:
已知sin
4
且0<a<π
-cos
α
的值
31
a
=√2/3
k是整数
求sin
llllllllllllllllllllllllllllllllllllllllllllllllll
514
π
kπ
π-a