Trigonometric Functions: Trigonometric Values in All Four Quadrants

Trigonometric Functions in Quadrants II - IV

The process to finding the sine and cosine in Quadrants II-IV is the same. It is very important to remember how these quadrants affect the x- and y-values when creating your special right triangles.

Quadrant one x and y both positive, Quadrant two x negative y positive, Quadrant three x and y both negative, Quadrant four x positive and y negative

In Quadrant I both the x- and y-values are positive.
In Quadrant II the x-value is negative while the y-value is positive.
In Quadrant III the x- and y-values are both negative.
In Quadrant IV the x-value is positive while the y-value is negative.