Hi, there--

The Problem--
If I drew a triangle that has 2 sides, 2 cm long and 2 angles that are 70 degrees. What kind of 
angle am I.

Solution--
Since we know the measures of two of the angles, we can kind that measure of the third angle.
Recall that the sum of the measures of the interior angles in any triangle is 180 degrees.
We have two 70 degree angles, so the third angle measures 40 degrees because 
70+70+40=180.

Notice that the two given side lengths are equal. We don't know the side length of the third.
If the triangle has three equal sides it is an equilateral triangle. However an equilateral triangle 
has three equal angles, too. We already know that our triangle has only two equal angles.

Therefore this triangle is an isosceles triangle.

Hope this helps!
Mrs.Figgy