On Wed, 20 Jul 2005 14:13:17 GMT, "David Lang"
wrote:

Hi

I'm building a pergola for my sister in law and my grasp of maths is failing
me.

The roof is an isosceles triangle, e.g. two sides the same and a base.

The angle at the apex is 140 degrees and the two base angles 20 degrees. I
know the size of the base.

How do I calculate the length of the two identical sides and the height from
base to apex?

I seem to recall something about "some officers have, curly auburn hair,
till old age" but I think that only applies to a right angle triangle.

Dave


Divide the triangle into 2 right angle triangles

You now have one side (1/2 the base), and all the angles.

So you look back as SOH CAH TOA

sin (angle) = length of side opposite angle / length of side next to
angle.

etc .........

Or you could reveal the length of the base, and some bright spake will
do this in their head for you.

Rick