Given: 

Find: 

(HINT: There is a line through C parallel to both
To find:
The value of
Given:
The given figure is,
Figure (1)
And,
Concept:
If two parallel lines are cut by a transversal then the angles of the alternate sides of transverse lines are equal.
Construction:
Draw a straight line passing through point
Figure (2)
Calculation:
Consider the figure (2),
Alternate angles are congruent
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