Trig Ratios

Sine (sin) of an angle is the ratio of the length of the opposite side to the length of the hypotenuse.

Cosine (cos) of an angle is the ratio of the length of the adjacent side to the length of the hypotenuse.

Tangent (tan) of an angle is the ratio of the length of the opposite side to the length of the adjacent side.

θ = 30° or θ = 150°.

The Pythagorean identity states that $$\text{sin}^2(\theta) + \text{cos}^2(\theta) = 1$$ .

Set the calculator to degree mode, input the angle, and press the sine function key.

Sine and cosine are co-functions: $$\text{sin}(\theta) = \text{cos}(90° - \theta)$$ .

The sine rule states that $$\frac{a}{\text{sin}(A)} = \frac{b}{\text{sin}(B)} = \frac{c}{\text{sin}(C)}$$ for any triangle.

You use the sine function.

$$\text{cos}(P) = \frac{q}{r}$$ .