Krishna
0

Step 1: Note down the given important points

              GIVEN: \tan 2A = \cot (A - 18\degree)

                             2A is an acute angle


Step 2: Write the equivalent complementary angle

              NOTE: \tan \theta = \cot (90\degree - \theta)


                         EXAMPLE: \tan 2A = \cot (90\degree - 2A) ........(1)


Step 3: Substitute the calculated value in the given equation and simplify


EXAMPLE:   \tan 2A = \cot(A - 18\degree) (given)


                         \cot (90\degree - 2A) = \sin (A - 18\degree) [since equation (1)]


                                 90\degree - 2A = A - 18\degree


                                         3A = 108\degree


                                       A =\frac{108}{3}


                                       A = 36 \degree