Today´s class 22/04/09

Today´s class, we started by checking our tests. After this, we started a new lesson, because we didn´t have to correct any homework.

At the beginning Mrs. Saatkamp explained us how to calculate the total measure of a polygon. To calculate it you have to be based in the diagonals formed, because then how many triangles will determine the total measure of the internal angles. Remember a triangle is 180 degrees total if you sum all the interior angles.

Then we learn a new theorem:

Theorem 10-1: Interior angle sum.

n=number of sides.

Si=Sum of interior angles.

Si=180(n-2) : Formula

Exterior angles:

Note: Every vertex has his own exterior angle.

Theorem 10-2: Exterior Angle sum.

Formula: Se=360

How to to prove it :

3x180=Si+Se

3x180=180(3-2)+Se

540=180+Se

360=Se

After this, we made two exercises about it in the board

For tomorrow we have hw! Pag 519#22-49 all!

I think it is all, see you guys tomorrow!