Geometry pg.62, #32

JanineG14 · **Joined:** Thu Feb 10, 2011 11:12 pm **Posts:** 10

I understand why the Pythagorean Theorem was used, but I don't understand where they are getting 192/2 = 361/2? or 212/2 = 441/2? Please explain.

I understand that 19^2 = 361 & 21^2 = 441. And then divide that by 2 to get the area in sq. in. and then finally find the difference b/w the two.

VP_Help · **Joined:** Thu Feb 12, 2009 6:32 pm **Posts:** 497

21 inch screen:

x^2 + x^2 = 21^2

2*x^2 = 21^2

x^2 = (21^2)/2 .... this is the area of the screen (the square of a side is the area)

19 inch screen:

(19^2)/2

difference: (21^2)/2 - (19^2)/2

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JanineG14 · **Joined:** Thu Feb 10, 2011 11:12 pm **Posts:** 10

Thanks for the reply, but I already understand that process. I'm not getting where they get 212/2 = 441/2 or 192/2 = 361/2. Where is the 212 & 192 coming from?

VP_Help · **Joined:** Thu Feb 12, 2009 6:32 pm **Posts:** 497

If the diagonal is 21 inches, we have an isosceles right triangle as follows:

x^2 + x^2 = 21^2, where x is a side of the square.

2 * x^2 = 21 * 21

x^2 = (21*21)/2 ... but since x is a side, side * side = area, so x^2 = area of the square

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Geometry pg.62, #32

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