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Solution: f(x)=cos x-(3)cosxsinx+1
f(x)=2[cos²x-(√3)cosxsinx+1]/2
f(x)=[2cos²x-2(√3)cosxsinx+2]/2
f(x)=[2cos²x-1-(√3)·2cosxsinx+3]/2
f(x)=[cos(2x)-(3)sin(2x)+3]/2
f(x)=(1/2)cos(2x)-[3)/2]sin(2x)+3/2
f(x)=sin(π/6)cos(2x)-cos(π/6)sin(2x)+3/2
f(x)=sin(π/6-2x)+3/2
f(x)=3/2-sin(2x-π/6)
The monotonically increasing interval of f(x) is: 2k - 2 2x - 6 2k + 2, where: k = 0, 1, 2, 3 ......, the same below.
2kπ-π/3≤2x≤2kπ+2π/3
kπ-π/6≤x≤kπ+π/3
That is, the monotonically increasing interval is found as: x [k - 6, k + 3].
With f(x)=3 2-sin(2x- 6) found above, the second question is simple.
Leave it to the landlord to practice.
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sin2x = three-thirds of the root number.
So sinxcosx = the root of sixths number three. Beg.
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f(x)=cos x-( beat3)cosxsinx+1
f(x)=2[cos²x-(√3)cosxsinx+1]/2
f(x)=[2cos²x-2(√3)cosxsinx+2]/2
f(x)=[2cos²x-1-(√3)·2cosxsinx+3]/2
f(x)=[cos(2x)-(3)sin(2x)+3]/2
f(x)=(1/2)cos(2x)-[3)/2]sin(2x)+3/2
f(x)=sin(π/6)cos(2x)-cos(π/6)sin(2x)+3/2
f(x)=sin(π/6-2x)+3/2
f(x)=3/2-sin(2x-π/6)
The monotonically increasing interval of f(x) is: 2k - 2 2x - 6 2k + 2, where: k = 0, 1, 2, 3 ......, the same below.
2kπ-π3≤2x≤2kπ+2π/3
K - 6 x Brother Raider K + 3
That is, the monotonically increasing interval is found as: x [k - 6, k + 3].
With f(x)=3 2-sin(2x- 6) found above, the second question is simple.
Leave it to the landlord to practice, 2, sin2x = three-thirds of the root number.
So sinxcosx = the root of sixths number three.
Find, 0, known function f(x) sin(2x- 6)+cos first dig x
If f(x) 1, find the value of sinx*cosx.
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Solution: (1) Using the difference angle formula and the double angle formula to simplify the function, f(x) = 3 2 sin2x + 1 2 can be obtained, and from f( )1, the mu book sin2 3 3 can be obtained, so that it can be found;
2) According to the monotonicity of the sinusoidal function, the monotonic interval of the function 1) f(x) sin2xcos can be obtained
6−cos2xsin
1+cos2x
2sin2x+
From f( )1, sin2 is obtained
3, so sin cos
2sin2θ=
2) When 2+2k 2x
2+2k, k z, i.e. x [
4+k,4+k],k z,f(x) monotonically increases So, the monotonically increasing interval of the function f(x) is [
4+k, 4+k],k z, monotonically reduced interval for (4+k, 3
4+kπ),k∈z.
1. The known function f(x) sin(2x 6 )+co s 2 x
1) If f( )1, find the value of sin cos;
2) Find the monotonic interval of the function f(x).
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f(x)=√3sinxcosx-cos²x+1/2=√3/2*sin2x-1/2(2cos²x-1)=√3/2*sin2x-1/2*cos2x=sin(2x-π/6)
1) Minimum positive period: t=2 2=
Let sin(2x-6) = 1
Then 2x- 6= 2+k, k z
The axis of symmetry equation is: x= 3+k2, kz(2), in abc.
f(a2)=sin(a-6)=1 2 a-6= 6 or 5 6
i.e. a= 3 or (rounded).
cosa=(b +c -a) 2bc=1 2 and bc=6
a²=b²+c²-6
2BC-66 then the minimum value of a is: 6
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f'(x)=1+2sinxcosx+cos2x-1=√2sin(2x+π/4)
1) The monotonic increase interval is 2k - 2=<2x+ 4<=2k + 2, i.e. k -3 8=2) 3 4=<2x+ 4<=3 2+ 4, the maximum value x= 4, f(x)=1
The minimum value x = 5 8, f(x) = - 2
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