Saturday

August 23, 2014

August 23, 2014

Posted by **Mary** on Sunday, May 22, 2011 at 3:18pm.

I know the perimeter is 40.

Now I need the area.

- Geometry -
**Reiny**, Sunday, May 22, 2011 at 4:30pmdraw the trap ABCD where AD=10,DC = 7, BC=17 and BA = 6

Draw AE parallel to DC, then AE=7 and BE = 7

We now have a parallelogram and a triangle.

Let's find angle AEB which is also angle C , call it Ø

by cosine law in triangle ABE

6^2 = 7^2 + 7^2 - 2(7)(7)cosØ

cosØ = .632653

Ø = 50.75386°

area = triangle + parallelogram

= (1/2)(7)(7)sin 50.75386 + (10)(7)sin50.75386

= 73.184

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