Question #ec539

1 Answer
P dilip_k
Dec 10, 2017

#LHS=sin20sin40sin80#

#=1/2*2sin20sin40sin80#

#=1/2(cos20-cos60)sin80#

#=1/4*2cos20sin80-1/2*1/2sin80#

#=1/4(sin100+sin60)-1/4sin80#

#=1/4(sin(180-80)+1/4*sin60)-1/4sin80#

#=1/4sin80+1/4*sqrt3/2-1/4sin80#

#=sqrt3/8=RHS#

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