Gambar 2.2
(i) Perhatikan Gambar 2.2 jika θ = 0°, Maka:
y = 0 dan x = r , sehingga
$$sin \space 0° = \frac{y}{r} =\frac{0}{r} = 0$$
$$cos \space 0° = \frac{x}{r} =\frac{r}{r} = 1$$
$$sin \space 0° = \frac{y}{x} =\frac{0}{r} = 0$$
(ii) Perhatikan kembali Gambar 2.2 jika θ = 90°, Maka:
x = 0 dan y = r , sehingga
$$sin \space 90° = \frac{y}{r} =\frac{r}{r} = 1$$
$$cos \space 90° = \frac{x}{r} =\frac{0}{r} = 0$$
$$tan \space 90° = \frac{y}{x} =\frac{r}{0} = ∞$$
Gambar 2.3
Gambar 2.4
Tabel 2. Sudut Istimewa
Fungsi Trigonometri | sudut | ||||
0° | 30° | 45° | 60° | 90° | |
sinus | $$0$$ | $$\frac{1}{2}$$ | $$\frac{1}{2}\sqrt{2}$$ | $$\frac{1}{2}\sqrt{3}$$ | $$1$$ |
cosinus | $$1$$ | $$\frac{1}{2}\sqrt{3}$$ | $$\frac{1}{2}\sqrt{2}$$ | $$\frac{1}{2}$$ | $$0$$ |
tangen | $$0$$ | $$\frac{1}{3}\sqrt{3}$$ | $$1$$ | $$\sqrt{3}$$ | $$∞$$ |