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# Calculus Review on Integrals

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1. Evaluate the following indefinite integrals:

See attached

2. On a dark night in 1915, a German zeppelin bomber drifts menacingly over London. The men on the ground train a spotlight on the airship, which is traveling at 90 km/hour, and at a constant altitude of 1 km. The beam of the spotlight makes an angle θ with the ground.

1. Draw a diagram of the situation.
2. When the airship is 3 kilometers from the spotlight, how fast is θ changing?
3. An electrical circuit consists of two parallel resistors, with resistances R1 and R2 respectively. The total resistance R of the circuit (measured in Ohms Ω) is specified by

See attached

https://brainmass.com/math/calculus-and-analysis/calculus-review-integrals-538803

#### Solution Preview

In these questions, we use the following formula:
∫▒〖x^n dx=x^(n+1)/(n+1)+c〗
(1)∫▒〖1/x^2 dx=-1/x+c〗
(2)∫▒〖e^(-x) dx=-e^(-x)+c〗
(3)∫▒〖sin⁡(t) cos⁡(t)dt=∫▒〖sin⁡(2t)/2 dt=sin⁡(2t)/4+c〗〗
Assume x=cos(t), dx=-sintdt,
Therefore, ∫▒〖sin⁡(t) cos⁡(t)dt=∫▒〖-xdx=-x^2/2+c〗〗=-(cost)^2/2+c
(4)∫▒〖s^(1/2) ds=s^(1/2+1)/(1/2+1)+c=2/3 s^(3/2)+c〗

2.)

First, we find out the relationship between x and θ,
Then we consider x and θ are functions of t,
After this assumption, we could do derivative on both sides for equation: tan(θ)=1/x
Tan(θ)=1/x,sec^2⁡〖θ*dθ/dt=-(1/x^2 dx)/dt〗
X=sqrt(3^2-1^2)=sqrt(8), dx/dt=90
Sec^2(θ)=1/(sqrt(8)/9)^2 =81/8
dθ/dt=-1/8*(81/8)*90=-113.91

1/R=1/R1+1/R2, when R1=80, R2=100, R=44.444
to find out the change rate for R,we consider ...

#### Solution Summary

The expert evaluates indefinite integrals in calculus. A diagram is drawn for a situation.

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