If sec (7α - 60°) = cosec (15° - 4α) then the value of cosα .

1  \(\frac{1}{\sqrt {3}}\)  \(\frac{3}{\sqrt {2}}\)  \(\frac{1}{\sqrt {2}}\)

\(\frac{1}{\sqrt {2}}\)

[Concept: sec A = cosec B, when A + B = 90°] Therefore, (7α - 60° + 15° - 4α) = 90° 3α = 135° α = 45° Put this value in find → ⇒ cos45° =  \(\frac{1}{\sqrt {2}}\)