The outer angle at the vertex A of the triangle ABC is 120 degrees, AC = BC = 25. Find the perimeter of the triangle.
| March 6, 2021 | education
In a triangle, the outer and inner angles at one vertex are adjacent.
The sum of adjacent angles is 180 °.
The inside angle at apex A is 180 ° -120 ° = 60 °.
In triangle ABC, the two sides are equal, so this triangle is isosceles by definition.
△ ABC – equilateral (AC = BC and <A = 60 °).
AC = BC = AB = 25.
P △ ABC = 25 * 3 = 75.
Answer: P △ ABC = 75.
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