In a triangle ABC, the angle B = 62 °, and the angle A is 20 ° less than the angle C. Find the degree measure of the angle A and the determinant of the form of the triangle ABC.
We take the value of the angle C as x, then:
x – 20 – angle value A.
Since the sum of the angles of the triangle is 180 °, we get the equation:
(x – 20) + 62 + x = 180;
2x = 180 – 42;
x = 138: 2 = 69 °.
Then the value of the angle A is equal to:
69 – 20 = 49 °.
Since all angles are less than 90 °, the triangle is acute-angled.
Answer: the required angle A is 49 °.
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