Here you can explore how the sign of the trigonometrical ratios change when the angles are in different quadrants. Remember the acronym "ASTC - All School Teachers Care! :)"
To find the sine, cosine and tangent values, we make use of the x and y coordinates (so that we can work with negative values) We fix the hypotenuse to be 1 unit so that the calculation is less tedious. so, the sine ratio is y/1 the cosine ratio is x/1 the tangent ratio is y/x ------------------------------------------------------------- Additional Exploration: Consider the sine of the following angles: sin 30 (first quadrant) sin (180 - 30) = sin 150 (second quadrant) sin (180 + 30) = sin 210 (third quadrant) sin (360 - 30) = sin 330 (fourth quadrant) What do you notice about the value, and sign of the resulting answers? Is there a pattern for the cosine and tangent ratios as well? :)