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cos(270/2)

Solução

cos (\frac{27 0 ^{\circ}}{2})

- \frac{1}{2}

Decimal

- 0.70710 \dots

Passos da solução

cos (\frac{27 0 ^{\circ}}{2})

Reeecreva usando identidades trigonométricas:

- \frac{1 + cos ( 27 0 ^{\circ} )}{2}

cos (\frac{27 0 ^{\circ}}{2})

Utilizar a identidade trigonométrica do arco metade:

cos (\frac{θ}{2}) = - \frac{1 + cos ( θ )}{2}

Utilizar a identidade trigonométrica do arco duplo

cos (2 θ) = 2 cos^{2} (θ) - 1

Substituir

θ

por

\frac{θ}{2}

cos (θ) = 2 cos^{2} (\frac{θ}{2}) - 1

Trocar lados

2 cos^{2} (\frac{θ}{2}) = 1 + cos (θ)

Dividir ambos os lados por

2

cos^{2} (\frac{θ}{2}) = \frac{( 1 + cos ( θ ) )}{2}

Square root both sides

Choose the root sign according to the quadrant of

\frac{θ}{2}

range [0, 9 0^{\circ}] [9 0^{\circ}, 18 0^{\circ}] [18 0^{\circ}, 27 0^{\circ}] [27 0^{\circ}, 36 0^{\circ}] quadrant I II III I V sin positive positive negative negative cos positive negative negative positive

cos (\frac{θ}{2}) = - \frac{( 1 + cos ( θ ) )}{2}

= - \frac{1 + cos ( 27 0 ^{\circ} )}{2}

= - \frac{1 + cos ( 27 0 ^{\circ} )}{2}

Reeecreva usando identidades trigonométricas:

cos (27 0^{\circ}) = 0

cos (27 0^{\circ})

Reeecreva usando identidades trigonométricas:

cos (18 0^{\circ}) cos (9 0^{\circ}) - sin (18 0^{\circ}) sin (9 0^{\circ})

cos (27 0^{\circ})

Escrever

cos (27 0^{\circ})

como

cos (18 0^{\circ} + 9 0^{\circ})

= cos (18 0^{\circ} + 9 0^{\circ})

Use a identidade de soma de ângulos:

cos (s + t) = cos (s) cos (t) - sin (s) sin (t)

= cos (18 0^{\circ}) cos (9 0^{\circ}) - sin (18 0^{\circ}) sin (9 0^{\circ})

= cos (18 0^{\circ}) cos (9 0^{\circ}) - sin (18 0^{\circ}) sin (9 0^{\circ})

Utilizar a seguinte identidade trivial:

cos (18 0^{\circ}) = (- 1)

cos (18 0^{\circ})

cos (x)

tabela de periodicidade com ciclo de

36 0^{\circ} n

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= (- 1)

Utilizar a seguinte identidade trivial:

cos (9 0^{\circ}) = 0

cos (9 0^{\circ})

cos (x)

tabela de periodicidade com ciclo de

36 0^{\circ} n

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= 0

Utilizar a seguinte identidade trivial:

sin (18 0^{\circ}) = 0

sin (18 0^{\circ})

sin (x)

tabela de periodicidade com ciclo de

36 0^{\circ} n

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= 0

Utilizar a seguinte identidade trivial:

sin (9 0^{\circ}) = 1

sin (9 0^{\circ})

sin (x)

tabela de periodicidade com ciclo de

36 0^{\circ} n

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= 1

= (- 1) \cdot 0 - 0 \cdot 1

Simplificar

= 0

= - \frac{1 + 0}{2}

Simplificar

= - \frac{1}{2}

arctan (49)

tan (\frac{25 π}{12})

\frac{tan ^{2} ( - \frac{5 π}{6} )}{sec ( - \frac{5 π}{6} ) + 1}

cos (2.5 π)

12.4 - 10 (0.5 π - arcsin (0.5) - 0.5 (1 - (0.5)^{2})^{\frac{1}{2}})