Solved on Feb 08, 2024

Evaluate the indefinite integral 2arccos(7x)149x2dx=\int \frac{2 \arccos (7 x)}{\sqrt{1-49 x^{2}}} d x = C$

STEP 1

Assumptions
1. We are given the indefinite integral 2arccos(7x)149x2dx\int \frac{2 \arccos (7 x)}{\sqrt{1-49 x^{2}}} d x to evaluate.
2. We will use substitution to simplify the integral.
3. We will use the fact that the derivative of arccos(u)\arccos(u) with respect to uu is 11u2\frac{-1}{\sqrt{1-u^2}}.
4. We will use the constant CC to represent the constant of integration.

STEP 2

Let's use substitution to simplify the integral. We will let u=arccos(7x)u = \arccos(7x). This means that x=cos(u)7x = \frac{\cos(u)}{7}.

STEP 3

We need to find dxdx in terms of dudu. To do this, we differentiate both sides of x=cos(u)7x = \frac{\cos(u)}{7} with respect to uu.
dxdu=17sin(u)\frac{dx}{du} = -\frac{1}{7}\sin(u)

STEP 4

Now we solve for dxdx.
dx=17sin(u)dudx = -\frac{1}{7}\sin(u) du

STEP 5

We substitute x=cos(u)7x = \frac{\cos(u)}{7} and dx=17sin(u)dudx = -\frac{1}{7}\sin(u) du into the integral.
2arccos(7x)149x2dx=2u149(cos(u)7)2(17sin(u))du\int \frac{2 \arccos (7 x)}{\sqrt{1-49 x^{2}}} d x = \int \frac{2 u}{\sqrt{1-49 \left(\frac{\cos(u)}{7}\right)^2}} \left(-\frac{1}{7}\sin(u)\right) du

STEP 6

Simplify the expression inside the square root.
149(cos(u)7)2=1cos2(u)1-49 \left(\frac{\cos(u)}{7}\right)^2 = 1 - \cos^2(u)

STEP 7

Recognize that 1cos2(u)1 - \cos^2(u) is equal to sin2(u)\sin^2(u).
1cos2(u)=sin2(u)1 - \cos^2(u) = \sin^2(u)

STEP 8

Substitute sin2(u)\sin^2(u) back into the integral.
2usin2(u)(17sin(u))du\int \frac{2 u}{\sqrt{\sin^2(u)}} \left(-\frac{1}{7}\sin(u)\right) du

STEP 9

Simplify the square root of sin2(u)\sin^2(u) to sin(u)\sin(u).
2usin(u)(17sin(u))du\int \frac{2 u}{\sin(u)} \left(-\frac{1}{7}\sin(u)\right) du

STEP 10

The sin(u)\sin(u) terms cancel out.
2u(17)du\int 2 u \left(-\frac{1}{7}\right) du

STEP 11

Simplify the integral.
27udu-\frac{2}{7} \int u \, du

STEP 12

Integrate uu with respect to uu.
27(u22)+C-\frac{2}{7} \left(\frac{u^2}{2}\right) + C

STEP 13

Simplify the constant factor.
17u2+C-\frac{1}{7} u^2 + C

STEP 14

Recall that u=arccos(7x)u = \arccos(7x) and substitute it back into the expression.
17(arccos(7x))2+C-\frac{1}{7} (\arccos(7x))^2 + C

STEP 15

Write the final answer.
2arccos(7x)149x2dx=17(arccos(7x))2+C\int \frac{2 \arccos (7 x)}{\sqrt{1-49 x^{2}}} d x = -\frac{1}{7} (\arccos(7x))^2 + C

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