Describing Triangles

a

Consider the given diagram.

We see that two sides in a triangle are congruent. According to the base angles theorem the angles opposite these sides are congruent. Thus, by the theorem $∠ A$ $≅$ $∠ C .$ Therefore, these two angles have the same measure.

As a result, we have that $m ∠ A = 4 8^{\circ} .$

b

The following triangle is given.

As we can see from the figure, $m ∠ A ≅ m ∠ C .$ Therefore, we can immediately identify the measure of $∠ A$ as $6 5^{\circ} .$

Describing Triangles 1.5 - Solution