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Question : 50 of 54
Marks:
+1,
-0
Solution:
sin4(‌)=‌−‌‌cos(‌)+‌‌cos(‌)‌‌.........(i) and
sin4(‌)=‌−‌‌cos(‌)+‌‌cos(‌) or
sin4(‌)=‌+‌‌cos(‌)−‌‌cos(‌) ........(ii)
Similarly,
sin4(‌)=‌−‌‌cos(‌)+‌‌cos(‌) or
sin4(‌)=‌+‌‌cos(‌)−‌‌cos(‌)‌‌.........(iii) Equation (i)
+( ii
)+( iii)
sin4(‌)+sin4(‌)+sin4(‌) =‌+‌‌cos(‌)−‌‌cos(‌)+‌‌cos(‌) −‌‌cos(‌)+‌‌cos(‌)−‌‌cos(‌) =‌+‌[cos(‌)+cos(‌)+cos(‌)] =‌+‌=‌ ∴a−b=21−16=5
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