দেখাই যে : \(\sec 70° \sin 20°+ \cos 20° cosec 70° = 2\)
\(sec 70° sin 20° +cos 20° cosec 70°\)
\(=sec(90°-20°) sin 20° +cos 20° cosec (90°-20°)\)
\(=cosec 20°sin 20° +cos 20° sec 20° [∵sec(90°-θ)=cosec θ \) এবং \(cosec (90°-θ)=secθ] \)
\(=\cfrac{1}{sin 20°} ×sin 20° +cos 20° ×\cfrac{1}{cos 20°} \)
\(=1+1\)
\(=2\) (প্রমাণিত)