# In an isosceles triangle ABC with base AC, the exterior angle at vertex C is 123 degrees. Find the angle ABC. Answer in degrees

In an isosceles triangle ABC with base AC, the exterior angle at vertex C is 123 degrees. Find the angle ABC. Answer in degrees
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Blaine Day
If the outer angle C is 123, then the inner angle is 180-123=57. Since the triangle is isosceles, angle A=C=57. The sum of the angles of a triangle is 180. 180-2*57=66.

empatiji2v
since the outer corner is adjacent to the angle DIA, then the angle DIA=180-123=57
and we know that angle BAC and angle DAB are equal, then BAC is also equal to 57 degrees
and to find ABC you need 180-(57+57)=180-144=66 degrees