Cos20+cos100+cos140=0
Answers
Answered by
201
cos20+cos100=2cos(100+20)/2cos(100-20)/2
=2cos(60)cos(40)
=2*1/2*cos(40)
=cos(40)
cos20+cos100+cos140=cos40 + cos140
=2cos(40+140)/2cos(40-140)/2
=2cos90cos50
=2*0*cos50
=0
=2cos(60)cos(40)
=2*1/2*cos(40)
=cos(40)
cos20+cos100+cos140=cos40 + cos140
=2cos(40+140)/2cos(40-140)/2
=2cos90cos50
=2*0*cos50
=0
Answered by
53
Answer:
LHS= cos20°+cos140°+cos100°
=2*cos 140+20/2*cos 140-20/2+cos100°
=2*cos80°*cos60°+cos(180-80)
=2*cos80*1/2-cos80°
=Cos80°-cos80°
=0
LHS=RHS proved.
Step-by-step explanation:
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