Can someone help me !!!

I'm having trouble with #2. I've got it down to the part where it would be the integral of 5cos^3(pheta)/sin(pheta). I'm not sur

Butoxors [25]

$\displaystyle\int\frac{\sqrt{25-x^2}}x\,\mathrm dx$

Setting $x=5\sin\theta$ , you have $\mathrm dx=5\cos\theta\,\mathrm d\theta$ . Then the integral becomes

$\displaystyle\int\frac{\sqrt{25-(5\sin\theta)^2}}{5\sin\theta}5\cos\theta\,\mathrm d\theta$
$\displaystyle\int\sqrt{25-25\sin^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta$
$\displaystyle5\int\sqrt{1-\sin^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta$
$\displaystyle5\int\sqrt{\cos^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta$

Now, $\sqrt{x^2}=|x|$ in general. But since we want our substitution $x=5\sin\theta$ to be invertible, we are tacitly assuming that we're working over a restricted domain. In particular, this means $\theta=\sin^{-1}\dfrac x5$ , which implies that $\left|\dfrac x5\right|\le1$ , or equivalently that $|\theta|\le\dfrac\pi2$ . Over this domain, $\cos\theta\ge0$ , so $\sqrt{\cos^2\theta}=|\cos\theta|=\cos\theta$ .

Long story short, this allows us to go from

$\displaystyle5\int\sqrt{\cos^2\theta}\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta$

to

$\displaystyle5\int\cos\theta\dfrac{\cos\theta}{\sin\theta}\,\mathrm d\theta$
$\displaystyle5\int\dfrac{\cos^2\theta}{\sin\theta}\,\mathrm d\theta$

Computing the remaining integral isn't difficult. Expand the numerator with the Pythagorean identity to get

$\dfrac{\cos^2\theta}{\sin\theta}=\dfrac{1-\sin^2\theta}{\sin\theta}=\csc\theta-\sin\theta$

Then integrate term-by-term to get

$\displaystyle5\left(\int\csc\theta\,\mathrm d\theta-\int\sin\theta\,\mathrm d\theta\right)$
$=-5\ln|\csc\theta+\cot\theta|+\cos\theta+C$

Now undo the substitution to get the antiderivative back in terms of $x$ .

$=-5\ln\left|\csc\left(\sin^{-1}\dfrac x5\right)+\cot\left(\sin^{-1}\dfrac x5\right)\right|+\cos\left(\sin^{-1}\dfrac x5\right)+C$

and using basic trigonometric properties (e.g. Pythagorean theorem) this reduces to

$=-5\ln\left|\dfrac{5+\sqrt{25-x^2}}x\right|+\sqrt{25-x^2}+C$

4 0

2 years ago

Read 2 more answers

A mixed number has a whole number part and a fractional part. <br>O A. True <br>O B. False

scoray [572]

Answer: True

Step-by-step explanation:

The statement that a mixed number has a whole number part and a fractional part is true.

The mixed number is made up of a whole number, and a proper fraction. A mixed number simply means a number that is between any two whole numbers. Examples of mixed numbers are 4¾, 7½ etc.

6 0

2 years ago

Given the sequence 4,16,64

umka2103 [35]

A. Geometric

b. a curve sloping steeply upwards (exponential)

c. nth term an = a1r^(n-1)

nth term = 4(4)^(n-1)

4 0

3 years ago

The larger of two numbers is 5 less than twice the smaller. Their sum is 43. Find the numbers.

tatyana61 [14]

Let's set up an equation.
smaller number = x
larger number = 2x - 5
Now set up the equation so that the larger number plus the smaller number adds up to 43.
x + 2x - 5 = 43
3x - 5 = 43 ( I added the x and 2x)
3x = 48 ( I added 5 to both sides)
x = 16 (I divided both sides by 3)

Now let's check it. Substitute 16 for every time there is an x.

16 + 2(16) - 5 = 43
16 + 32 - 5 = 43
48 - 5 = 43
43 = 43
It checks. x is equal to 16, so that means:
smaller number = 16
larger number = 27

Hope this helps =)

5 0

2 years ago

A father is now 38 years older than his son. Ten years ago he was twice as old

harkovskaia [24]

The father is 48 and the son is 20

3 0

2 years ago