In an early femoral triangle ABC with a base AC, the angle ABC is 46 degrees.

In an early femoral triangle ABC with a base AC, the angle ABC is 46 degrees. Find the external angle at the vertex C.

An isosceles triangle is a triangle in which the sides are equal, as well as the angles at the base are equal:

∠А = ∠С.

In order to find the value of the outer angle, you need to find all the inner corners of the triangle.

Since in any form of triangles, the sum of all angles is 180º, and the angle opposite to the base is 46º, then:

∠А = ∠С = (180º – ∠В) / 2;

∠А = ∠С = (180º – 46º) / 2 = 67º.

The outside corner of a triangle is the angle adjacent to the inside corner at one vertex. Since the sum of the outer and inner angles at one vertex make up the unfolded angle, which is 180º, then:

φ = 180º – ∠С;

φ = 180º – 67º = 113º.

Answer: the external angle at the apex ∠С is equal to 113º.