Answer:

Step-by-step explanation:

A TRIANGLE is a polygon having 3 sides and 3 angles.  

A REGULAR POLYGON is a polygon which all sides and all interior angles are equal.  

There are 6 CLASSIFICATIONS OF TRIANGLES

1. Right Triangle

- has a 90 deg angle

2. Equilateral Triangle

- has 3 congruent sides and 3 congruent angles of which are 60 deg each.

3. Isosceles Triangle

- has 2 equal sides and angles.

4. Scalene Triangle

-All sides and angles are different from one another

5. Acute Triangle

-has one of its angles lesser than 90 deg.

6. Obtuse Triangle

-has one of its angles greater than 90 deg.

Recall that the SUM OF INTERIOR ANGLES of a triangle is equal to 180 deg.  

In the above problem, it is stated that the triangle is isosceles. Therefore, its 2 sides and angles are equal, or its base angles are equal.  

We assume A as the measure of each base angle, giving us 70 deg, A, and A as the angles. Adding all the angles and equating them to 180 deg, would give us

70 deg + A + A = 180 deg

Simplifying

70 deg + 2A = 180 deg

2A = 180  - 70

2A = 110

A = 55 deg

Therefore, each base angle measures 55 degrees.

Refer to the provided illustration for better understanding.

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