Apply the quotient rule, which is:
dxdg(x)f(x)=g2(x)−f(x)dxdg(x)+g(x)dxdf(x)
f(x)=x2+sin(x) and g(x)=cot(2x).
To find dxdf(x):
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Differentiate x2+sin(x) term by term:
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Apply the power rule: x2 goes to 2x
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The derivative of sine is cosine:
dxdsin(x)=cos(x)
The result is: 2x+cos(x)
To find dxdg(x):
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There are multiple ways to do this derivative.
Method #1
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Rewrite the function to be differentiated:
cot(2x)=tan(2x)1
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Let u=tan(2x).
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Apply the power rule: u1 goes to −u21
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Then, apply the chain rule. Multiply by dxdtan(2x):
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Rewrite the function to be differentiated:
tan(2x)=cos(2x)sin(2x)
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Apply the quotient rule, which is:
dxdg(x)f(x)=g2(x)−f(x)dxdg(x)+g(x)dxdf(x)
f(x)=sin(2x) and g(x)=cos(2x).
To find dxdf(x):
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Let u=2x.
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The derivative of sine is cosine:
dudsin(u)=cos(u)
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Then, apply the chain rule. Multiply by dxd2x:
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The derivative of a constant times a function is the constant times the derivative of the function.
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Apply the power rule: x goes to 1
So, the result is: 2
The result of the chain rule is:
2cos(2x)
To find dxdg(x):
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Let u=2x.
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The derivative of cosine is negative sine:
dudcos(u)=−sin(u)
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Then, apply the chain rule. Multiply by dxd2x:
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The derivative of a constant times a function is the constant times the derivative of the function.
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Apply the power rule: x goes to 1
So, the result is: 2
The result of the chain rule is:
−2sin(2x)
Now plug in to the quotient rule:
cos2(2x)2sin2(2x)+2cos2(2x)
The result of the chain rule is:
−cos2(2x)tan2(2x)2sin2(2x)+2cos2(2x)
Method #2
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Rewrite the function to be differentiated:
cot(2x)=sin(2x)cos(2x)
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Apply the quotient rule, which is:
dxdg(x)f(x)=g2(x)−f(x)dxdg(x)+g(x)dxdf(x)
f(x)=cos(2x) and g(x)=sin(2x).
To find dxdf(x):
-
Let u=2x.
-
The derivative of cosine is negative sine:
dudcos(u)=−sin(u)
-
Then, apply the chain rule. Multiply by dxd2x:
-
The derivative of a constant times a function is the constant times the derivative of the function.
-
Apply the power rule: x goes to 1
So, the result is: 2
The result of the chain rule is:
−2sin(2x)
To find dxdg(x):
-
Let u=2x.
-
The derivative of sine is cosine:
dudsin(u)=cos(u)
-
Then, apply the chain rule. Multiply by dxd2x:
-
The derivative of a constant times a function is the constant times the derivative of the function.
-
Apply the power rule: x goes to 1
So, the result is: 2
The result of the chain rule is:
2cos(2x)
Now plug in to the quotient rule:
sin2(2x)−2sin2(2x)−2cos2(2x)
Now plug in to the quotient rule:
cot2(2x)(2x+cos(x))cot(2x)+cos2(2x)tan2(2x)(x2+sin(x))(2sin2(2x)+2cos2(2x))