## area of a triangle

Geometric formulae, word problems, theorems and proofs, etc.
Edmca
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Joined: Mon Mar 16, 2015 3:18 pm
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### area of a triangle

Hi, I am have trouble with this problem. Find the area of triangle with angles 45-15-120. The side across from the 120 degree angle is 10. I need to solve without Trig. Similar problems have found 30-60-90 or 45-45-90 triangles in problem and used them to find the solution. But I am stumped....Ed

FWT
Posts: 153
Joined: Sat Feb 28, 2009 8:53 pm

### Re: area of a triangle

Hi, I am have trouble with this problem. Find the area of triangle with angles 45-15-120. The side across from the 120 degree angle is 10. I need to solve without Trig. Similar problems have found 30-60-90 or 45-45-90 triangles in problem and used them to find the solution. But I am stumped....Ed
How did they solve the ones with 30-60-90 triangles and 45-45-90 triangles? Can you extend one of the sides forming the 120-degree angle, drop the perpendicular from the vertex on that side, and form a 30-60-90 triangle along that side, and do anything with that? Like, for a start, the height of the 30-60-90 triangle would be the height of the 15-45-120 triangle, too.