\(tan 2A = cot (A - 30° )\) হলে, \(sec ( A \) \(+ 20°)\) এর মান নির্ণয় করো।
Madhyamik 2023
\(tan 2A = cot (A - 30° )\)
বা, \(tan 2A =tan[90° - (A - 30° )]\)
বা, \(2A =90° - (A - 30° )\)
বা, \(2A =90° - A + 30° \)
বা, \(2A+A =120° \)
বা, \(A=40° \)
\(\therefore sec (A + 20°) = sec (40°+ 20°)\)
\( =sec 60° =2\)