Home >Computer Tutorials >Computer Knowledge >Let the function fx root 3 coswx^2 sinwx coswx a where w 0
f(x)=√3(coswx)^2 sinwxcoswx a
=root 3 (cos2wx 1)/2 sin2wx/2 a
= sin(2wx π/3) √3 / 2 a,
The abscissa of the first lowest point on the right side of the y-axis of the image of f(x) is 7π/6.
So when x=7π/6, 2w*7π/6 π/3=3π/2,
W=1/2.
So f(x)= sin(x π/3) √3 / 2 a,
X∈[-π/3,5π/6], then x π/3∈[0,7π/6],
The minimum value of sin(x π/3) is sin7π/6=-1/2,
The minimum value of sin(x π/3) √3 / 2 a is -1/2 √3 / 2 a,
So -1/2 √3 / 2 a=√3,
a=(√3 1)/2.
y=root number 3sinxcox cos^2x
=root number 3sinxcox (1/2-1/2cos2x)
=(root 3/2) sin2x 1/2-1/2co2x
=sin2xcospie/6-cos2xsinpie/6 1/2
=sin(2x-pie/6) 1/2
-pie/3-2pie/3-pie/2 and because sin(2x-pie/6) 1/2=-root number 3/2 1/2
sin(2x-pie/6)=-root number 3/2
Because sin (pie/2-pie/6)=cos pie/6=-cos root number 3/2
2x Pie/6=2/ Pie Pie/2 Pie/6
x=pie/4
y=sin(2x-pie/6) 1/2 abscissa is compressed to the original 1/2
g(x)=(4x-PI/6) 1/2 translation ∏/6 units, and finally translation upwards 1 unit
y=sin(4x-5/6 faction) 3/2 interval, write it yourself
Explanation "√3" means root number 3, pai is π
Solution: (1) Let t=sinwx, then y=-√3t^2 t (√3-a) According to the meaning of the question: t=sinwx image passes the origin and pai/6 is the first maximum value point
So, the period of t=sinwx is T=(pai/6)*4=(2pai)/3
According to the period formula: T=(2pai)/3=(2pai)/w, so w=3
(2)For t=sin3x,-paiy=-√3t^2 t (√3-a) axis of symmetry t=1/(2√3)
y=-√3t^2 t (√3-a) first increases and then decreases on [-1,1], so the minimum value of y is y(-1) or y(1)
And y(-1)=-√3 (-1) √3-a=-1-a ; y(1)=-√3 1 √3-a=1-a then y(min)= -1-a=√3
a=-1-√3
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