volume using cross-sections

Calculus
Tutor: None Selected Time limit: 1 Day

May 18th, 2015

The limits of integration are from x=-pi/2 to x=pi/2.

r_ext(x) = 5, r_int(x) = 5*sqrt(cos(x)).

V = pi*int_from(-pi/2)_to(pi/2)[r_ext^2(x) - r_int^2(x)]dx =

pi*int_(-pi/2)_(pi/2)[25 - 25*cos(x)]dx =

pi*25*[x - sin(x)]_(-pi/2)_(pi/2) =

pi*25*[(pi/2-(-pi/2)) - (sin(pi/2)-sin(-pi/2))] =

25pi*(pi - 2).

May 18th, 2015

thank you, but look how they want the answer... this is an exampleIMG_8910.jpg

May 18th, 2015

Sorry, but the picture you uploaded now is different from the initial!
5sqrt(cos(x)) and 3sqrt(cos(x)) make different figures.

May 19th, 2015

The approximate decimal value is 179,32 (cubic units).

May 19th, 2015

No, sorry, 57.08.

May 19th, 2015

And again calculator ... the correct answer is 89.66.

May 19th, 2015

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May 18th, 2015
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May 18th, 2015
May 27th, 2017
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