sin 55* + cos 81* = cos 21*
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sin 51 + cos 81 = cos 21
L.H.S. = sin 51 + cos 81
= sin 51 + sin 9
[coz cos(90 - x) = sin x]
= 2 sin 30 cos 21
{coz sin A + sin B = 2 sin [(A+B)/2] cos [(A-B)/2]}
= cos 21 = R.H.S.
HENCE PROVED !!!!!!!
L.H.S. = sin 51 + cos 81
= sin 51 + sin 9
[coz cos(90 - x) = sin x]
= 2 sin 30 cos 21
{coz sin A + sin B = 2 sin [(A+B)/2] cos [(A-B)/2]}
= cos 21 = R.H.S.
HENCE PROVED !!!!!!!
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