In triangle ABC, bisectors Am and BN are drawn, intersecting at point K, and the angle AKN = 58gr. Find: angle ACB.
September 11, 2021 | education
| Let’s denote the angles of the triangle as follows:
angle A = x;
angle B = y;
angle C = z;
Then we get that the following equality is true:
x + y + z = 180 °;
Since we know from the condition that the AKN angle is 58 °, the BKA angle will be 180 ° – 58 ° = 122 °.
Let’s take a closer look at the AKB triangle:
angle AKB = 122 °;
angle KAB = 1/2 angle BAN = x / 2;
angle KBA = 1/2 angle CBA = y / 2.
Then we get, which is true for the triangle BKA:
angle AKB + angle KAB + angle KBA = 180 °;
122 ° + x / 2 + y / 2 = 180 °;
x / 2 + y / 2 = 180 ° – 122 °;
(x + y) / 2 = 58 °;
x + y = 58 ° * 2 = 116 °.
We substitute this value into the expression with three unknowns and we get:
116 ° + z = 180 °;
z = 180 ° – 116 °;
z = 64 °.
Answer: angle ACB = 64 °.
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