provethat:cos18=√2sin27
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i think the question u wrote is wrong
Cos18°-sin18°=√2sin27°
Cos18- Sin18= cos18 - cos72
= -2×sin(18+72)/2 × sin (18-72)/2 (using CosC-CosD)
= -2 sin45×sin(-27) 2sin45sin27
=√2×sin27
Cos18°-sin18°=√2sin27°
Cos18- Sin18= cos18 - cos72
= -2×sin(18+72)/2 × sin (18-72)/2 (using CosC-CosD)
= -2 sin45×sin(-27) 2sin45sin27
=√2×sin27
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