A circle is described around the quadrilateral CDEF, the angle CDF = 80 °, the angle DEC = 30 °. What is the DCF angle?
March 31, 2021 | education
| In the quadrilateral CDEF, inscribed in a circle, the angles based on the same arc are equal, that is, <DFC = <DEC = 30 °. Consider a triangle DCF with <DFC = 30 °; a <DEC = 80 °.
Then you can define <DCF = 180 ° – <DFC – <DEC = 180 ° – 30 ° – 80 ° = 70 °.
Answer: <DCF = 70 °.
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