The value of angle ∠DEC = 60 degree.
The complete question is
In the given the figure above, m∠BAC = 64° and m∠CBA = 56°.
Part I: Find the m∠DEC.
Part II: Explain the steps you took to arrive at your answer. Make sure to justify your answer by identifying any theorems, postulates, or definitions used.
What is a Triangle ?
A triangle is a polygon with three sides and three vertices and three angles.
As it is given that
AB || CD
Let BC be the transversal , then
∠CBA = ∠DCB (alternate opposite angles)
∠DCB = 56 degree
As the sum of opposite interior angle sis equal to exterior angle therefore ∠ ECB = 120 degree
∠DCE = 120-56 = 64 degree
BC || DE
∠EDC = ∠DCB = 56 degree (alternate opposite angles)
Sum of all the interior angles of a triangle is equal to 180 degree
56 +64+∠DEC = 180
∠DEC = 60 degree.
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