sin40° + sin20° = cos10°
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Answer:
Step-by-step explanation:
Take cos10° on L.H.S
It comes,
sin40°+sin20°-cos10° = 0
L.H.S
=sin40° +sin20°- cos10°
Using sinC+sinD= 2sin(C+D)/2 cos(C-D)/2
={2sin(40°+20°)/2 cos(40°-20°)/2} - cos10°
=(2sin30° cos10°) - cos10°
=cos10° (2sin30° - 1)
=cos10°(2×1/2 - 1)
=cos10° (1-1)
=cos10° (0)
=0
=R.H.S
LHS = RHS
Hence proved
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Hope it helps...
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