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The sine of any angle

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The cosine of any angle

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The tangent of any angle

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Tangent is positive

Sine is positive All are positive

Remember CAST

We can use CAST to remember in which quadrant each of the three ratios are positive.

Cosine is positive

3rd quadrant

2nd quadrant 1st quadrant

4th quadrant

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Positive or negative?

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The third quadrant

What are the trigonometric ratios for –110°?

sin –110 = sin250 = – sin70

In the third quadrant only tangent is positive.

–110° is also +250°. We use the 70° angle shown in the diagram and CAST.

tan –110 = tan250 = tan70

cos –110 = cos250 = –cos70

70° 110°

C

AS

T

0°180°

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Equivalents