Wat is de oplossingenverzameling
van de goniometrische vergelijking
2 cos x + 1 = 0   ?
( in zestigedelige graden) 		A.   { 60° + k.180°}
B.   { ±120° + k.360°}
C.   {  ±60° + k.360°}
D.   { ±120° + k.360°}
E.   { ±135° + k.360°}
A    B    C    D    E

[ 5-0562 - op net sinds 21.6.16-(e)-4.11.2023 ]

Translation in   E N G L I S H

What is the solution set of
2 cos x + 1 = 0   ?
(in degrees) 		A.  { 60° + k.180°}
B.  { ±120° + k.360°}
C.  {  ±60° + k.360°}
D.  { ±120° + k.360°}
E.  { ±135° + k.360°}

Oplossing - Solution

    2.cos x + 1 = 0
⇔ cos x = −½
⇔ cos x = −cos 60°
⇔ cos x = cos 120°
⇔ x = 120° + k.360°  ∨  x = −120° + k.360°