Question

Cos70 +cos 50 - Sin 80​

Answer 1

Oie, tudo bom?

= cos(70°) + cos(50°) - sin(80°)

= 2cos([70° + 50°]/2)cos([70° - 50°]/2) - sin(80°)

= 2cos([120°]/2)cos([20°]/2) - sin(80°)

= 2cos(60°)cos(10°) - sin(80°)

= 2 . 1/2 . cos(10°) - sin(80°)

= cos(10°) - sin(80°)

= cos(90° - 80°) - sin(80°)

= sin(80°) - sin(80°)

= 0

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