In the triangle ABC A = 100 °, B = 30 ° at the vertex C, find the outer angle.

In the ABC triangle it is known:

∠ А = 100 °;

∠ B = 30 °.

Find the outer angle at vertex C.

1) The sum of all the angles of the triangle is 180 °, then we find the third angle C.

∠ С = 180 ° – ∠ А – ∠ В = 180 ° – 100 ° – 30 ° = 80 ° – 30 ° = 50 °;

2) Find the outer angle at vertex C.

In order to find the outer angle at the vertex C, you need to subtract the angle C from 180 °.

180 ° – 50 ° = 130 °.

Answer: 130 ° is the outer angle at apex C.