SOLUTION: Divide the circle area (with radius r) with one cut (one tendon) in a ratio of 1:2.

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Question 1194629: Divide the circle area (with radius r) with one cut (one tendon) in a ratio of 1:2.
Answer by Edwin McCravy(20063) About Me  (Show Source):
You can put this solution on YOUR website!
I'm not sure what you want here.  But I'll do enough of it to get you
so you can finish.

Let AB be the chord which divides the area of the circle so that
the area above AB is 1/3 of the area of the circle A=pi%2Ar%5E2.
Then the area below AB will be 2/3 of the area of the circle. Then
they will be in the ratio 1:2



We draw in two radii to A and B.



First we find the area of the sector AOB ("piece of pie") 

Area%22%22=%22%22%28theta%2F360%29%2Api%2Ar%5E2

In this case, theta=%22%3CAOB%22

Area%22%22=%22%22%28%22%3CAOB%22%2F360%29%2Api%2Ar%5E2

We must subtract the area of triangle AOB to get the area
above AB.

If a triangle has two sides with lengths x and y, and the 
angle between these two sides is θ degrees, then the area 
of the triangle is given by the equation 

Area%22%22=%22%22+expr%281%2F2%29x%2Ay%2Asin%28theta%29

In this case, x and y both equal the radius r, and theta=%22%3CAOB%22

Area%22%22=%22%22+expr%281%2F2%29r%2Ar%2Asin%28%22%3CAOB%22%29
Area%22%22=%22%22+expr%281%2F2%29r%5E2%2Asin%28%22%3CAOB%22%29

The area above AB is

%28%22%3CAOB%22%2F360%29%2Api%2Ar%5E2%22%22-%22%22+expr%281%2F2%29r%5E2%2Asin%28%22%3CAOB%22%29

This must equal 1/3 of the area, which is expr%281%2F3%29%2Api%2Ar%5E2 

So the equation is 

%28%22%3CAOB%22%2F360%29%2Api%2Ar%5E2%22%22-%22%22+expr%281%2F2%29r%5E2%2Asin%28%22%3CAOB%22%29%22%22=%22%22expr%281%2F3%29%2Api%2Ar%5E2 

We divide through by r2

%28%22%3CAOB%22%2F360%29%2Api%22%22-%22%22+expr%281%2F2%29%2Asin%28%22%3CAOB%22%29%22%22=%22%22expr%281%2F3%29%2Api

You can only solve that for %22%3CAOB%22 with technology.

I used a TI-84 Plus.  I got 149.27417o

Use that to find whatever else your teacher wants. 

Edwin