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\(\cos\theta=\cfrac{x}{\sqrt{x^2+y^2}}\)
বা, \(\sec\theta=\cfrac{\sqrt{x^2+y^2}}{x}\)
বা, \(\sec^2\theta=\left(\cfrac{\sqrt{x^2+y^2}}{x}\right)^2\)
বা, \(\sec^2\theta=\cfrac{x^2+y^2}{x^2}\)
বা, \(\sec^2\theta-1=\cfrac{x^2+y^2}{x^2}-1\)
বা, \(\tan^2\theta=\cfrac{x^2+y^2-x^2}{x^2}\)
বা, \(\tan^2\theta=\cfrac{y^2}{x^2}\)
বা, \(\tan\theta=\cfrac{y}{x}\)
বা, \(\cfrac{\sin \theta}{\cos \theta}=\cfrac{y}{x}\)
বা, \(x \sin \theta =y \cos \theta\) (প্রমাণিত)