Question

If $tan2A=cot(A-{18}^{\circ })$, then value of $A$ is ((A - 18) & 2A are acute angle)

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

Given, $tan2A=cot(A-{18}^{\circ }$)

$\Rightarrow tan2A=tan(90-(A-{18}^{\circ })$

$\Rightarrow tan2A=tan({108}^{\circ }-A)$

$\Rightarrow 2A={108}^{\circ }-A$

$\Rightarrow 3A={108}^{\circ }$

$\Rightarrow A={36}^{\circ }$