Q.If \( \tan 2A = \cot (A - 30^\circ) \), then find the value of \( \sec (A + 20^\circ) \).

Given: \[ \tan 2A = \cot (A - 30^\circ) \] \[ \Rightarrow \tan 2A = \tan \left[90^\circ - (A - 30^\circ)\right] \Rightarrow 2A = 90^\circ - (A - 30^\circ) \Rightarrow 2A = 90^\circ - A + 30^\circ \Rightarrow 2A + A = 120^\circ \Rightarrow A = 40^\circ \] \[ \therefore \sec (A + 20^\circ) = \sec (40^\circ + 20^\circ) = \sec 60^\circ = 2 \]
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