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