Math, asked by rakshha, 5 months ago

show that cos80°+cos40°-cos20°=0

Answers

Answered by soleclarkstella

1

Answer:

cos80°+cos40°-cos20°

cos80°+cos40°

cosA+cosB= 2 cos[(A+B)÷2] cos [(A-B)÷2]

cos80°+cos40°= 2cos(120/2) cos(40/2)

cos80°+cos40°= 2cos(60) cos 20

= 2×1/2×cos20

= cos20°

cos80°+cos40°-cos20°= cos20°-cos20°

= 0

Hence, proved

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