The Quadrants (CAST)

Quadrants I, II, III  and  IV

(They are numbered in a counter-clockwise direction)

• In  Quadrant I  both x and y are positive,
• in  Quadrant II  x is negative (y is still positive),
• in  Quadrant III  both x and y are negative, and
• in  Quadrant IV  x is positive again, and y is negative.

In the first quadrant, the values for sin, cos, and tan are positive.
In the second quadrant, the values for sin are positive only.
In the third quadrant, the values for tan are positive only.
In the fourth quadrant, the values for cos are positive only.

We can use a mnemonic like  CAST  or  A ll  S tudents  T ake  C alculus to remember the signs in the 4