লিমিট

নিচের সীমার মান কোনটি? limθ0cot(π2θ)cos(π2θ)θ2\lim _{\theta \rightarrow 0} \frac{\cot \left(\frac{\pi}{2}-\theta\right)-\cos \left(\frac{\pi}{2}-\theta\right)}{\theta^{2}}

limθ0cot(π2θ)cos(π2θ)θ2=limθ0tanθsinθθ2=limθ0tanθ(1cosθ)θ2=limθ0tanθθ×limθ02sin2θ2θ \begin{array}{l} \lim _{\theta \rightarrow 0} \frac{\cot \left(\frac{\pi}{2}-\theta\right)-\cos \left(\frac{\pi}{2}-\theta\right)}{\theta^{2}} \\ =\lim _{\theta \rightarrow 0} \frac{\tan \theta-\sin \theta}{\theta^{2}} \\ =\lim _{\theta \rightarrow 0} \frac{\tan \theta(1-\cos \theta)}{\theta^{2}} \\ =\lim _{\theta \rightarrow 0} \frac{\tan \theta}{\theta} \times \lim _{\theta \rightarrow 0} \frac{2 \sin ^{2} \frac{\theta}{2}}{\theta} \end{array}

=1×limθ0(sinθ2θ2)22×14×limθ0θ=1×1×12×0=0 (Ans.)  \begin{array}{l} =1 \times \lim _{\theta \rightarrow 0}\left(\frac{\sin \frac{\theta}{2}}{\frac{\theta}{2}}\right)^{2} 2 \times \frac{1}{4} \times \lim _{\theta \rightarrow 0} \theta \\ =1 \times 1 \times \frac{1}{2} \times 0=0 \text { (Ans.) } \end{array}

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