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January 16th, 2015, 05:13 PM   #1
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Finding angles

I'm trying to find the 4 angles that are circled in the image. I need to make these cuts, but don't know how to find the angle. Any help is appreciated.

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January 16th, 2015, 08:11 PM   #2
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Top 2 angles are equal, so are bottom 2 angles (else no solution possible).

Extend upwards until a triangle is formed.
Let height of the triangle = 52+h.

Then, by similarity:
h / (119/16) = (h + 52) / 27 ; note that 1/2(14 7/8) = 119/16
Solve for h.
Then use Law of Sines to calculate angles.
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January 17th, 2015, 06:36 AM   #3
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Btw, if you're not familiar with the stuff I've used,
but simply want a way to "cut properly", then
draw your diagram to scale (use graph paper),
and simply measure the angles.
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January 17th, 2015, 01:29 PM   #4
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Slightly modified the image;

Observe that angle ADC + angle DAE = 180 degrees.
Alternative method, construct DE such thet DE is perpendicular to AB (and CD).

Now, AE is (27''-14.875'')/2 and we have a right triangle with known sides so we can find the angles.
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