Answer:
a) The measure of the base angle is 30°.
Step-by-step explanation:
The angle formed by the vertex of two equal sides in an isosceles triangle is called a VERTEX ANGLE.
Also, the other two base angles are equals they are opposite to equal sides.
Now, let us assume that the base angle = a
So, by ANGLE SUM PROPERTY:
Sum of all angles of triangle = 180°
⇒ 120° + a + a = 180°
or, 2 a = 180 -120 = 60°
or, a = 60/2 = 30°
or, a = 30°
Hence, the measure of the base angle is 30°.
