已知向量m=(sinA,cosA)n=(1,-2)mxn=0
2个回答
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1.
m*n=sinA-2cosA=0
tanA=sinA/cosA=2
2.
f(x)=cos2x+tanAsinx
=cos2x+2sinx
=1-2(sinx)^2+2sinx
=(3/2)-2(sinx - 1/2)^2
-1<=sinx<=1
-3/2 <= sinx - 1/2 <= 1/2
0<= (sinx - 1/2)^2 <= 9/4
所以： (3/2)-2*(9/4)<=f(x)<=3/2
-3<=f(x)<=3/2
值域:[-3,3/2]
m*n=sinA-2cosA=0
tanA=sinA/cosA=2
2.
f(x)=cos2x+tanAsinx
=cos2x+2sinx
=1-2(sinx)^2+2sinx
=(3/2)-2(sinx - 1/2)^2
-1<=sinx<=1
-3/2 <= sinx - 1/2 <= 1/2
0<= (sinx - 1/2)^2 <= 9/4
所以： (3/2)-2*(9/4)<=f(x)<=3/2
-3<=f(x)<=3/2
值域:[-3,3/2]
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