Question

The angle of vertex of an isoceles triangle is 100.find its base angle

Answer 1

let base angles be angle a and angle c
let angle B be 100 degrees
as base angles of isosceles triangle are equal
therefore angle a equal to angle c
by angle sum property,
angle a + angle B + angle c is 180
100 + 2 angle a is 180
2 angle a is 80
angle a is 40
therefore base angles are 40 degrees

Answer 2

100 + x+x =180
2x = 80
x = 40...hence base angles are 40 40