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Example 6:. If A, B, C are the interior angles of interior ABC, prove that



               Solution: In  ABC, we have,
                                 o
               A + B + C = 180             [Angle sum property of triangle]













               Hence, proved.


               NCERT Exercise 8.3


               Q 3. tan 2A = cot (A - 18°) , Where 2A is an acute angle, Find the value of A.

               Answer: tan 2A = cot (90° – 2A) = cot (A - 18°)     (  as cot (90° – A) = tan A )

                   (90° – 2A) = (A - 18°)


                        3A = 108°
                        A = 36°








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