# Straight through the top. angle C in triangle ABC, a straight line CK || AB is drawn; angle KCB = 42 °

October 1, 2021 | education

| **Straight through the top. angle C in triangle ABC, a straight line CK || AB is drawn; angle KCB = 42 °. Find angles A and B in triangle ABC**

We consider straight lines AB and CK, they are parallel by the condition of the problem. Line BC is a secant for these two lines.

The angles KСВ and ABC are cross-lying angles with parallel AB, СK and secant BC, we conclude:

∠KСВ = ∠ABC = 42 °.

Triangle ABC is rectangular, we find the second acute angle A:

∠ A = 90 ° – ∠ ABC = 90 ° – 42 ° = 48 °.

Answer: the degree measure of angle A is 48 °, angle B is 42 °.

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