Question

The angle of vertex of an isoceles triangle is 100 degrees. Fine the base angle.

Answer 1

Answer:

Angle of vertex of an isosceles triangle(angle 1)

=100°

It is given that the triangle is isosceles,this means that the other two angles are same.Let angle2 be equal to angle3 angle 2 be the base angle.

So, by angle sum property of a triangle:

Angle 1+angle2+Angle 3=100°

100°+angle2+angle2=180°

2angle2=180°-100°

2angle2=80°

Angle 2=80/2=40°

So, the base angle =angle 2=40°

Answer 2

Answer:

Step-by-step explanation:  Sum of the angles of a triangle = 180°

Because isosceles triangle as two sides equal then it must also have two angles which are equal. Clearly 100 cannot be the one of the equal side because 100 x 2 = 200 which is greater than 180°.

So 100 + 2 x the equal angle = 180°

Let the equal angle be a.

100 + 2a = 180

→ 100 + 2a  - 100 = 180 - 100

→ 2a =80

→ 2a ÷ 2 = 80 ÷ 2

→ a = 40

So the base angle is 40 !

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