The Natural Philosopher wrote:
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


An isocelese triangle is two right angled ones stuck together,
conceptually.
YOU work it out.

I can't work out how a single triangle can actually form a roof at
all...

Never seen a lean to?