Solved on Jan 31, 2024

Evaluate the indefinite integral (312sec24x)dx\int(3 - 12 \sec^2 4x) dx.

STEP 1

Assumptions
1. We need to integrate the function 312sec2(4x)3 - 12\sec^2(4x) with respect to xx.
2. The integral of a constant aa with respect to xx is axax.
3. The integral of sec2(u)\sec^2(u) with respect to xx is tan(u)\tan(u), provided uu is a function of xx and du/dxdu/dx is a constant.

STEP 2

We will split the integral into two separate integrals to simplify the calculation.
(312sec2(4x))dx=3dx12sec2(4x)dx\int(3 - 12\sec^2(4x))dx = \int 3dx - \int 12\sec^2(4x)dx

STEP 3

First, we integrate the constant 33 with respect to xx.
3dx=3x\int 3dx = 3x

STEP 4

Next, we need to integrate 12sec2(4x)-12\sec^2(4x) with respect to xx. We notice that the inner function is 4x4x, so we will need to use a substitution to solve this integral.

STEP 5

Let u=4xu = 4x. Then, dudx=4\frac{du}{dx} = 4, which means dx=du4dx = \frac{du}{4}.

STEP 6

Substitute uu and dxdx into the integral.
12sec2(4x)dx=12sec2(u)du4\int 12\sec^2(4x)dx = \int 12\sec^2(u) \frac{du}{4}

STEP 7

Simplify the integral by taking the constant 12/412/4 outside the integral.
12sec2(u)du4=3sec2(u)du\int 12\sec^2(u) \frac{du}{4} = 3\int \sec^2(u) du

STEP 8

Now, integrate sec2(u)\sec^2(u) with respect to uu.
sec2(u)du=tan(u)\int \sec^2(u) du = \tan(u)

STEP 9

Substitute back the value of uu to get the integral in terms of xx.
tan(u)=tan(4x)\tan(u) = \tan(4x)

STEP 10

Combine the results from the integrals of the constant and the sec2(4x)\sec^2(4x) term.
3x3tan(4x)3x - 3\tan(4x)

STEP 11

Add the constant of integration CC to the result, as the integral of a function is indefinite.
3x3tan(4x)+C3x - 3\tan(4x) + C

STEP 12

Write the final answer.
(312sec2(4x))dx=3x3tan(4x)+C\int(3 - 12\sec^2(4x))dx = 3x - 3\tan(4x) + C
The integral of 312sec2(4x)3 - 12\sec^2(4x) with respect to xx is 3x3tan(4x)+C3x - 3\tan(4x) + C.

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