Nilai Trigonometri
1. Diberikan bahwa $\sin 70^\circ = p$ dan $\cos 70^\circ = q$. Kita diminta mencari nilai dari $\cos 110^\circ \times \cot 160^\circ + \sin 200^\circ$.\n\n2. Gunakan identitas sudut terkait:\n- $\cos 110^\circ = \cos (180^\circ - 70^\circ) = -\cos 70^\circ = -q$\n- $\cot 160^\circ = \cot (180^\circ - 20^\circ) = -\cot 20^\circ$\n- $\sin 200^\circ = \sin (180^\circ + 20^\circ) = -\sin 20^\circ$\n\n3. Substitusi ke dalam ekspresi:\n$$\cos 110^\circ \times \cot 160^\circ + \sin 200^\circ = (-q) \times (-\cot 20^\circ) + (-\sin 20^\circ) = q \cot 20^\circ - \sin 20^\circ$$\n\n4. Kita tahu $\cot 20^\circ = \frac{\cos 20^\circ}{\sin 20^\circ}$, sehingga:\n$$q \cot 20^\circ - \sin 20^\circ = q \frac{\cos 20^\circ}{\sin 20^\circ} - \sin 20^\circ = \frac{q \cos 20^\circ - \sin^2 20^\circ}{\sin 20^\circ}$$\n\n5. Karena $p = \sin 70^\circ$ dan $q = \cos 70^\circ$, dan $70^\circ + 20^\circ = 90^\circ$, maka $\sin 70^\circ = \cos 20^\circ = p$ dan $\cos 70^\circ = \sin 20^\circ = q$. Jadi:\n$$q \cos 20^\circ = \sin 20^\circ \cos 20^\circ$$\n$$\sin^2 20^\circ = \sin^2 20^\circ$$\n\n6. Substitusi kembali:\n$$\frac{q \cos 20^\circ - \sin^2 20^\circ}{\sin 20^\circ} = \frac{\sin 20^\circ \cos 20^\circ - \sin^2 20^\circ}{\sin 20^\circ} = \frac{\sin 20^\circ (\cos 20^\circ - \sin 20^\circ)}{\sin 20^\circ} = \cos 20^\circ - \sin 20^\circ$$\n\n7. Karena $\cos 20^\circ = p$ dan $\sin 20^\circ = q$, hasil akhirnya adalah:\n$$p - q$$\n\nJadi, nilai dari $\cos 110^\circ \times \cot 160^\circ + \sin 200^\circ$ adalah $p - q$.