Question

Provide steps to the equation. :)

Answer 1

• C. 90°

Explanation:

Angle ABC is the sum of angles ABD and DBC as per angle addition postulate

As per given we have isosceles triangles ABD and BCD

ADC is straight angle, therefore:

• 2x + x = 180°
• 3x = 180°
• x = 60°

Triangle ABD

• ∠BAD = ∠ABD = 1/2(180° - 2x) = 1/2(180° - 120°) = 1/2(60°) = 30°

Triangle BCD

• ∠BDC =∠ BCD = x = 60°
• ∠DBC = 180° - 2*60° = 180° - 120° = 60°

So the angle ABC

• ∠ABC = ∠ABD + ∠DBC
• ∠ABC = 30° + 60° = 90°