B-5. Show that : cos 2 0 cos = sin ...
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B-5. Show that : cos 2 0 cos = sin 5 - cos 3 0 cos 90 sin 50 sin 2

JEE/Engineering Exams
Maths
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( begin{aligned} &=12: 9: 2 cos 2 theta cos frac{theta}{2}-cos 3 theta cos frac{9 theta}{2} &=frac{1}{2}left(frac{2 cos 2 theta cos theta+2 cos 3 theta cos 2 theta}{2}right) {=frac{1}{2}left(cos left(2 theta+frac{theta}{2}right)+cos left(2 theta-frac{theta}{2}right)-cos left(frac{3 theta+9 theta}{2}right)-cos left(frac{3 theta-90}{2}right)right.}{left.frac{1}{2}left(cos frac{5 theta}{2}+cos frac{3 theta-cos 15 theta-cos 3 theta}{2}-frac{1}{2}right) frac{(cos 5 theta-cos 15 theta)}{2}right)}{=frac{1}{2} times 2 sin left(frac{left.frac{15 theta}{2}-frac{5 theta}{2}right) sin left(frac{15 theta+frac{5 theta}{2}}{2}right)}{2}right.} &=sin theta cdot sin left(frac{50}{2}right) end{aligned} )
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