In an isosceles triangle ABC with base BC∠B = 40 degrees. Find the adjacent angle at vertex C

Given:

isosceles triangle ABC,

ВС – base,

AB and AC – lateral sides,

angle B = 40 degrees,

the KCA angle is adjacent to the ACB angle.

Find the degree measure of the KSA angle -?

Solution:

Consider an isosceles triangle ABC. Therefore, the sides in it are equal to each other and the angles at the base are also equal, that is, the angle B = angle C = 40 degrees.

Knowing that the sum of the degree measures of the angles is 180 degrees, then

angle ACK = 180 – angle ACB;

angle ACK = 180 – 40;

angle ACK = 140 degrees.

Answer: 140 degrees.