Sign of Trigonometric Functions/Mnemonic

Mnemonic
It has been suggested that it is difficult to remember which of the three main trigonometric functions (sine, cosine and tangent) are positive and which are negative in which quadrants of the Cartesian plane.

Hence the invention of mnemonics to aid their correct identification.


 * Quadrants-Mnemonic.png

It is noted that:
 * in the first quadrant, all of sine, cosine and tangent) are positive.


 * in the second quadrant, of these only the sine function is positive.


 * in the third quadrant, of these only the tangent function is positive.


 * in the fourth quadrant, of these only the cosine function is positive.

Hence, by placing each of the initial letters of $\text {Cosine}$, $\text {All}$, $\text {Sine}$ and $\text {Tangent}$ in each of the four quadrants, starting in the second quadrant and moving anticlockwise around the origin, the word $\text {CAST}$ is spelled.