The correct option is D812 (cos25∘+cos285∘)+(cos210+cos280∘)+⋅⋅⋅+cos245∘+⋅⋅⋅ =(cos25∘+sin25∘)+(cos210∘)+⋅⋅⋅+cos245∘+⋅⋅⋅[usingcos(90∘−θ)=sinθ] =1+1+1+(8times)+12=812
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Q5
Without using trigonometric tables, prove that:
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