If tan (theta) = (frac{m^2 – n^2}{2mn}) find sec(theta)

A.
(frac{m^2 + n^2}{(m^2 – n^2)}) 
B.
(frac{m^2 + n^2}{2mn}) 
C.
(frac{mn}{2(m^2 + n^2)}) 
D.
(frac{m^2n^2}{2(m^2 – n^2)})
Correct Answer: Option B
Explanation
Tan (theta) = (frac{m^2 – n^2}{2mn})
(frac{text{Opp}}{text{Adj}}) by pathagoras theorem
= Hyp^{2} = Opp^{2} + Adj^{2}
Hyp^{2} = (m^{2} – n^{2}) + (2mn)^{2}
Hyp^{2} = m^{4} – 2m^{2}n^{4} – 4m^{2} – n^{2}
Hyp^{2} = m^{4} + 2m^{2} + n^{2}n
Hyp^{2} = (m^{2} – n^{2})^{2}
Hyp^{2} = (frac{m^2 + n^2}{2mn})