Monday

January 26, 2015

January 26, 2015

Posted by **ms** on Monday, September 16, 2013 at 4:10am.

s= Int (0 to 2pi) of Sqrt(4a^2cos^2 theta+4a^2sin^2 theta)d theta

=Int (0 to 2pi)2a*Int theta d theta

=2a(2pi-0)=4a*pi

Book shows 2a*pi. Am I wrong somewhere?

- calculus -
**ms**, Monday, September 16, 2013 at 4:12amSorry, slight typo. Please reasd it as Int (0 to 2pi)2a*Int d theta=2a(2pi-0)=4a*pi

- calculus -
**Steve**, Monday, September 16, 2013 at 4:32amwell, you know from the equation that the circle has radius a, so its circumference is 2a*pi.

r = 2acosθ

r^2 = 2arcosθ

x^2+y^2 = 2ax

(x-a)^2 + y^2 = a^2

Now, as for the integration, your formula is correct, but as θ goes from 0 to 2pi, the circle is traced twice. So, you should only integrate from 0 to pi.

Do a plot and you can see why this is so.

- calculus -
**ms**, Monday, September 16, 2013 at 4:44amThanks a lot for guiding,please.

**Answer this Question**

**Related Questions**

Math Trig Please Help!!! - Find exact values for all the solutions to the ...

Trig - Solve the following interval 0<_ (less than or equal to)0(Theta)<...

pre calc - find all solutions on 0 is greater than or equal to theta < 2pi ...

math - find all solutions on 0 is greater than or equal to theta < 2pi cos ...

calculus - Find complete length of curve r=a sin^3(theta/3). I have gone thus- (...

Precalculus check answers help! - 1.) Find an expression equivalent to sec theta...

Precalculus check answers help! - 1.) Find an expression equivalent to sec theta...

math - knowing that 2(theta) can be written as theta + theta, find the ...

Precalculus(NEED HELP ASAP PLEASE!!) - PLEASE HELP!! csc(theta)= -3/2 3pi/2 <...

Calculus - I wanted to confirm that I solved these problems correctly (we had to...