By theorem: the sum of all the angles of a triangle is 180 degrees.
A + B + C = 180 °.
Let’s find the sum of two known angles B and C:
40 + 70 = 110 °.
From the sum of all the angles of the triangle, subtract the sum of the angles B and C and find what the angle A is equal to.
180 ° – 110 ° = 70 °.
Answer: Angle A is 70 °.
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