The height CF is drawn in an isosceles triangle CDE with base CE. Find the angle ECF if the angle is D = 54 degrees.
| May 22, 2021 | education
By condition, the angle D is known.
Find the angle at the base:
∠ DCE = ∠ DEC = (180 ° – ∠ CDE) / 2 = (180 ° – 54 °) / 2 = 126 ° / 2 = 63 °.
Consider a right-angled triangle CFE and find the unknown angle ECF:
∠ ECF = 90 ° – ∠ DEC = 90 ° – 63 ° = 27 °.
Answer: The degree measure of the ECF angle is 27 °.
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