Main/central vertex

ABC is an isosceles triangle with base BC and main vertex A. The angle at vertex A is 18°. What will be the size of the angle at vertex B?

Correct answer:

B =  81 °

Step-by-step explanation:

A=18 C=B A+B+C=180  A+B+B=180 18+B+B=180  2B=162  B=81=81

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