Hi, i am hoping that someone could help me or give me a hint for the follwing question...i will show what I have done so far(adsbygoogle = window.adsbygoogle || []).push({});

The area of a quarter circle given is

Integral sqrt(25-x^2) dx

Use the substitution x = 5 sinu to evaluate this def integral exactly an show that your answer is consistent with area pi*r^2 with radius r

firstly i did dx/du = 5cos u

then i said:

Integral 5sqrt(1-sin^2u).5cosu du

Integral 5cosu.5cosu

Integral 25 cos^2u du

Integral 25(1+cos2u)/2

Integral 25/2 +25cos2u/2

and well the problem i am having is that i dont know how to get the u =5sin u to SUB into the intergal so i can solve it (ie i can SUB u into cos2u...it doesnlt work)

so hopefully someone could point me in a better diretion to solve this??

thanks heaps!!

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# Homework Help: Prooving Area of Circle Equation

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