My Math Forum Final question of the day !. Circles !

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January 26th, 2013, 10:57 AM   #1
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Final question of the day !. Circles !

Last question I am stuck on.Many thanks to everyone who helped me today.

Question is attached
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 Circle Question.tiff (35.4 KB, 158 views)

January 26th, 2013, 10:58 AM   #2
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Re: Final question of the day !. Circles !

Note if that attachment does not work this one should
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 Circle Question 1.pdf (11.1 KB, 15 views)

 January 26th, 2013, 11:26 AM #3 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Final question of the day !. Circles ! In your attachment, none of the area is shaded.
January 26th, 2013, 11:29 AM   #4
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Re: Final question of the day !. Circles !

Good Point!

Right Here is attachment with it shaded
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 Circle Question 2.pdf (10.1 KB, 9 views)

 January 26th, 2013, 11:53 AM #5 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Final question of the day !. Circles ! Have you identified what it is you need to know in order answer this question?
 January 26th, 2013, 12:01 PM #6 Member   Joined: Jan 2013 Posts: 47 Thanks: 0 Re: Final question of the day !. Circles ! Yes , The area formula for circles pi R squared Which was, 4pi for each You would then need to work out the area of the semicircle then subtract area of 2 circles from semicircle, But how would you work out the area of the semicircle ?
 January 26th, 2013, 06:02 PM #7 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Final question of the day !. Circles ! What I meant was, we need to know the diameter (or radius) of the semi-circle. Hint: Consider the right half of the diagram only. Now, draw a radius of the semi-circle through the center of the smaller circle. Use the Pythagorean theorem to determine the radius of the semi-circle. What do you find?
 January 26th, 2013, 11:17 PM #8 Member   Joined: Jan 2013 Posts: 47 Thanks: 0 Re: Final question of the day !. Circles ! Not much ! I presume the radius of the semicircle is the hypotenuse but how would I find out the lengths of the other 2 sides ???
January 26th, 2013, 11:34 PM   #9
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Re: Final question of the day !. Circles !

Consider the diagram:

[attachment=0:1b13qg7k]circleswithinsemicircle.jpg[/attachment:1b13qg7k]

So, what must the radius of the semicircle be?
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 circleswithinsemicircle.jpg (11.7 KB, 102 views)

January 27th, 2013, 01:56 AM   #10
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Quote:
 Originally Posted by gazing600000 7. The diagram shows two equal circles, both of radius 2 cm, inside a semicircle. Find the shaded area. You can leave ? in your answer.
For those who can't view the diagram, the shaded area is presumably the area that is within the semicircle but not within the two smaller circles that the semicircle encloses. The preceding post shows half of the diagram, thereby showing how the smaller circles are positioned within the semicircle.

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