Hi Myntherun,

Think of the terminal side of an angle rotating through the 4 quadrants.

If the terminal side is in QI, tan, sin and cos are all positive.

If the terminal side is in QII, sin is positive while tan and cos are negative.

If the terminal side is in QIII, tan is positive while sin and cos are negative.

If the terminal side is in QIV, cos is positive while tan and sin are negative.