Negative angles (1 Viewer)

[Green Yoda]

for the question solve for 2cos(2x)+1=0 for -π<=x<=π
the answers are x= -60,-120,60,120 (cbf writing in radians on here)
But my question is why does x=-60 when x is positive in the 4th quadrant?

 

[Shuuya]

for the question solve for 2cos(2x)+1=0 for -π<=x<=π
the answers are x= -60,-120,60,120 (cbf writing in radians on here)
But my question is why does x=-60 when x is positive in the 4th quadrant?

A negative angle just means that it's being counted in the clockwise direction from 0, rather than anticlockwise.

 

[leehuan]

for the question solve for 2cos(2x)+1=0 for -π<=x<=π
the answers are x= -60,-120,60,120 (cbf writing in radians on here)
But my question is why does x=-60 when x is positive in the 4th quadrant?

We wish to solve cos(2x) = -1/2
Over the degrees boundaries of -180deg ≤ x ≤ 180deg

This is equivalent to saying -360deg ≤ 2x ≤ 360deg

So we have
2x = -240deg, 2x = -120deg, 2x = 120deg, 2x = 240deg

Which becomes x = ±60deg, ±120deg

 

[fluffchuck]

negative angles do not necessarily mean negative value.

x=-60 when you add 360 is x=300 which is a positive number but it means the same thing, it's still in the 4th quadrant.

If I haven't made it clear, please say so, I'm not the best with explaining sorry