I encountered an question of calculation of volume.

The following is a part of the solution.

I don't know why the highlighted sinθ has an absolute value sign.

Can anyone explain to me? Thank you.

Attachment 26621

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- Jan 20th 2013, 08:44 AMhappymatthematicsabsolute value with sinθ
I encountered an question of calculation of volume.

The following is a part of the solution.

I don't know why the highlighted sinθ has an absolute value sign.

Can anyone explain to me? Thank you.

Attachment 26621 - Jan 20th 2013, 12:31 PMHallsofIvyRe: absolute value with sinθ
Because $\displaystyle \sqrt{a^2}= |a|$, not a.

For example, $\displaystyle \sqrt{(-2)^2}= \sqrt{4}= 2$, not $\displaystyle -2$. - Jan 20th 2013, 04:54 PMhappymatthematicsRe: absolute value with sinθ
Thank you, HallsofIvy.