Question

sin40° + sin20° = cos10°​

Answer 1

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...