Q. 29 In the figure, ABCD is a parallelogram and CDE is a triangle. ∠EDA=52∘ and ∠BCE=19∘. Find ∠DEC.
Identify Relationship: Identify the relationship between angles in a parallelogram; opposite angles are equal.
Angle Equality in Parallelogram: Since ABCD is a parallelogram, angle ABC equals angle CDA.
Calculate Angle CDA: Angle CDA is supplementary to angle EDA because they are consecutive angles in a parallelogram, so angle CDA =180∘−52∘=128∘.
Calculate Angle DEC: In triangle CDE, angles CDE and EDA are supplementary to angle DEC, so angle DEC = 180∘−angle CDE−angle EDA.
Find Angle CDE: But we need to find angle CDE first, which is equal to angle BCE since they are alternate interior angles created by a transversal cutting parallel lines BC and DE.
Substitute and Calculate DEC: So, angle CDE= angle BCE=19∘.
Substitute and Calculate DEC: So, angle CDE=BCE=19°.Now we can find angle DEC by substituting the values we have: angle DEC=180°−128°−19°=33°.
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