In which quadrants does the cosine decrease

Sine and cosine on the unit circle

Reading time: 5 min

We want to read all sine and cosine values ​​from the unit circle. We'll explain how to do this below.

We see that with the unit circle the Opposite cathete (see value on the y-axis) den Sine value indicates and the Affiliate (see value on the x-axis) the Cosine value.

We remember:

We can just as well say that the point on the circular line carries the sine and cosine values ​​in its coordinates:

We remember:

In the unit circle, the opposite side corresponds to the sine value and the adjacent side to the cosine value, paying attention to the signs. The following also applies: The coordinates of point P on the circular line of the unit circle indicate cosine value (x) and sine value (y).

Angle with sine and cosine positive or negative

Depending on the angle chosen, we also get negative values ​​for sine, cosine and tangent. Here is an overview with the four quadrants:

II. Quadrant
I. Quadrant
III. quadrant
IV. Quadrant

We see: sine is positive in the 1st and 2nd quadrant ("top"), cosine is positive in the 1st and 4th quadrant ("right") and the tangent is in the 1st and 3rd Quadrant positive. We get negative values ​​for sine in III. and IV. quadrants ("below"), for cosines in the II. and III. Quadrant ("left") and for the tangent in the 2nd and 4th quadrant.