Theorem 8.4: In a parallelogram, opposite angles are equal Given: A parallelogram ABCD with AC as its diagonal To prove: ∠ A = ∠ C & ∠ B = ∠ D Proof: Opposite sides of parallelogram is parallel So, AB ∥ DC and AD‖∥ BC Adding (1) and (2) ∠BAC + ∠DAC = ∠DCA + ∠ BCA ∠BAD = ∠DCB Similarly, we can prove ∠ADC = ∠ABC Hence Proved.

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.