Without using trigonometric tables, evaluate the following: `(sec37^0)/(cos e c53^0)+2cot15^0cot25^0cot45^0cot75^0cot65^0(sin^2 18^0+sin^2 72^0)`

Explanation

` sec x={cosec}(frac{pi}{2}-x) ;`

` {cotx}=tan (frac{pi}{2}-x) ; `
`cos x=sin (frac{pi}{2}-x)`


`frac{sec 37^{circ}}{sec 37^{circ}}+2 tan 75^{circ} tan 65^{circ} cot 75^{circ} cot 65^{circ}-3(sin ^{2} 18^{circ}+cos ^{2} 18^{circ})=1+2-3=0`