函数y=12sin(2x+π6)+5sin(π3-2x)的最大值为(  ) A.6+532 B.17 C.13 D.12

问题描述:

函数y=12sin(2x+

π
6
)+5sin(
π
3
-2x)的最大值为(  )
A. 6+
5
3
2

B. 17
C. 13
D. 12

y=12sin(2x+

π
6
)+5sin(
π
3
-2x)=12sin(2x+
π
6
)+5sin(
π
2
-
π
6
-2x)
=12sin(2x+
π
6
)+5cos(2x+
π
6

=13[
12
13
sin(2x+
π
6
)+
5
13
cos(2x+
π
6
)]
=13sin(2x+
π
6
+φ)(φ为辅助角)
则当2x+
π
6
+φ=2kπ+
π
2
,k为整数,y取最大值13.
故选C.