#
All sin cos tan rule

The abbreviation for 'all sin cos tan' rule in trigonometry is **ASTC**. It can be memorized as

**"All Students Take Calculus".**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.

## 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.

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