A S T C Rule:

A S T C rule:

    The abbreviation for 'all sin cos tan' rule in trigonometry is ASTC . The first letter of the first word in this phrase is 'A'. This may be taken to indicate that all trigonometric ratios in the first quadrant are positive . The first letter of the second word S indicates that sine and its reciprocal are positive in the 2nd quadrant. The first letter of the third word T indicates that tangent and its reciprocal is positive in the third quadrant. The first letter of the last word C indicates that cosine and its reciprocal are positive in the fourth quadrant.

                    

A S T C

                                                                                           

All Sin Cos Tan Rule:

1) When $\Theta$ lies in the first quadrant then all trigonometric ratios are positive.
2) When $\Theta$ lies in the second quadrant then sine and cosecant are positive other trigonometric ratios sin ,cosec, tan and cot are negative.
3) When $\Theta$ lies in the third quadrant then tangent and cotangent are positive other trigonometric ratios sin ,cosec, tan and cot are negative.
4) When $\Theta$ lies in the fourth quadrant then cosine and secant are positive other trigonometric ratios sin ,cosec, tan and cot are negative.