Question

me ajudem nessa questão trigonométrica, só preciso da letra B.​

Answer 1

Resposta:

b) cos 50= cos(90-40)

cos(a-b)=cosacosb+senasenb

cos(90-40)=cos90cos40+sen90sen40=0+sen40

cos 50= cos(90-40)=sen40=sen(20+20)

sen(a+b)=senacosb+senbcosa

sen(20+20)=sen20cos20+sen20cos20=2sen20cos20

cos 50= cos(90-40)=sen40=sen(20+20)=2sen20cos20

sen2a=2senacosa

sen20=sen2.10=2sen10cos10=2.0,17.0,98=0,3332

cos2a=cos²a-sen²a

cos20=cos2.10=cos²10-sen²10=(0,98)²-(0,17)²=0,9315

cos 50= cos(90-40)=sen40=sen(20+20)=2sen20cos20=2.0,3332.0,9315=0,62