Can anyone tell me what the cosine of -pi/3 is and why?

Answer 1

cos(-&pi/3)

Since cosine is an even function, cos(-x) = cos(x), so this is the same as

cos(&pi/3)

This is where we use our knowledge of the unit circle. The answer is 1/2.

Answer 2

1/2
Since you have a negative value, you need to consider a rotation in the clockwise direction. pi/3 = 60deg
The coordinate of the point on the unit circle centered at the origin gives you the values of cosine and sine. x is cos and y is sine. If you are not familiar with the concept, you can consider the case of a right triangle with angles 60=pi/3, 30=pi/6, 90=pi/2 with corresponding sides 1, sqrt of 3, and 2.
cos60=adjacent side/hypotenuse=1/2
But cos(-pi/3)=cos(pi/3)

Answer 3

It is indeed 1/2 the value is +ve because the answer is in the fourth quadrant. The cos of -pi/3 is the same as cos pi/3, however their sin values are opposite.

Answer 4

It's 1/2, I assume you're using radian measure.

The negative just gives a direction of a rotation, indicating whether clock, or counter-clockwise.

It IS 1/2 because if you make a right triangle with this angle on the inside, the ratio of the length of the leg nearest this angle to the length of the hypoteneuse is 1/2, always.

Answer 5

pi is in radian, pi radian=180/pi degree,
so -pi/3=-60 degree
the cosine of -60 degree is 1/2 and since it's cosine (-60), don't worry about the minus, so
the cosine of -pi/3 is 1/2

Answer 6

- π / 3 = - 60° = 300° = 10 (π/6)
Is in 4th quadrant and the cosine is the same as cos π/3
cos (π/3) = 1 / 2.
Cos(- π/3) = 1 / 2

Answer 7

+ 1/2.

Draw the picture. You know--the unit circle.

Answer 8

that's a half of one...just