Evaluate:
cos 55°sin 35°\dfrac{\text{cos 55°}}{\text{sin 35°}}sin 35°cos 55° + cot 35°tan 55°\dfrac{\text{cot 35°}}{\text{tan 55°}}tan 55°cot 35°
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cos 55°sin 35°+cot 35°tan 55°=cos (90° - 45°)sin 35°+cot (90° - 55°)tan 55°=sin 45°sin 35°+tan 55°tan 55°=sin45°sin35°+tan55°tan55°=1+1=2\dfrac{\text{cos 55°}}{\text{sin 35°}} + \dfrac{\text{cot 35°}}{\text{tan 55°}}\\[1em] = \dfrac{\text{cos (90° - 45°)}}{\text{sin 35°}} + \dfrac{\text{cot (90° - 55°)}}{\text{tan 55°}}\\[1em] = \dfrac{\text{sin 45°}}{\text{sin 35°}} + \dfrac{\text{tan 55°}}{\text{tan 55°}}\\[1em] = \dfrac{\cancel{sin 45°}}{\cancel{sin 35°}} + \dfrac{\cancel{tan 55°}}{\cancel{tan 55°}}\\[1em] = 1 + 1\\[1em] = 2sin 35°cos 55°+tan 55°cot 35°=sin 35°cos (90° - 45°)+tan 55°cot (90° - 55°)=sin 35°sin 45°+tan 55°tan 55°=sin35°sin45°+tan55°tan55°=1+1=2
Hence, cos 55°sin 35°+cot 35°tan 55°\dfrac{\text{cos 55°}}{\text{sin 35°}} + \dfrac{\text{cot 35°}}{\text{tan 55°}}sin 35°cos 55°+tan 55°cot 35° = 2.
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