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Mathematics 10 Online
OpenStudy (anonymous):

please help? WILL GIVE MEDAL

OpenStudy (anonymous):

OpenStudy (anonymous):

@whpalmer4

OpenStudy (whpalmer4):

|dw:1393284435941:dw| Can you find the area of the semicircle?

OpenStudy (anonymous):

2 is the radius, isnt it? the whole circle is 12.56 (i think) so /2 = 6.28

OpenStudy (anonymous):

(i hope, lol)

OpenStudy (whpalmer4):

Yes, \(r = 2\) so area of entire circle is \(A = \pi r^2 = \pi(2)^2 = 4\pi\) so area of the semicircle is \(2\pi = 6.28\) for this problem's purposes. Now do you agree that the shaded area is the area of the semicircle - the area of the triangle inscribed?

OpenStudy (whpalmer4):

Can you find the area of that triangle?

OpenStudy (anonymous):

i agree the shaded part of the circle is part of the semicircle, yes. (i dont understand the triangle part) I'm getting 4. Idk if that's right... the base is 4 and it states the height is 2

OpenStudy (whpalmer4):

The area of the shaded region is what's left after you take the semi-circle and cut away the triangle, right? The area of the triangle is \[A=\frac{1}{2}b*h = \frac{1}{2}2*4 = 4\] So the area of the shaded region is area of the semi-circle - the area of the triangle =

OpenStudy (anonymous):

I'm still confused...... 4 doesn't make sense to me.

OpenStudy (whpalmer4):

If you look at the triangle you should be able to see that if you take the one on the right, rotate it a bit and nestle it up with the one on the left, hypotenuse to hypotenuse, you'll get a square with side length 2 and thus area 4. |dw:1393457298143:dw|

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