Answered

Find the exact value of [tex]\sin 165^{\circ}[/tex].

A. [tex]\frac{\sqrt{2}+\sqrt{4}}{4}[/tex]
B. [tex]\frac{\sqrt{2}-\sqrt{6}}{4}[/tex]
C. [tex]\frac{\sqrt{6}+\sqrt{2}}{4}[/tex]
D. [tex]\frac{\sqrt{6}-\sqrt{2}}{4}[/tex]

Please select the best answer from the choices provided:
A
B
C
D



Answer :

To find the exact value of [tex]\(\sin 165^{\circ}\)[/tex], we can use trigonometric identities and angle decomposition.

1. First, note that [tex]\(165^{\circ}\)[/tex] can be written as [tex]\(180^{\circ} - 15^{\circ}\)[/tex].

2. Using the identity [tex]\(\sin(180^{\circ} - x) = \sin x\)[/tex], we get:
[tex]\[ \sin 165^{\circ} = \sin 15^{\circ} \][/tex]

3. Next, we need to find the exact value of [tex]\(\sin 15^{\circ}\)[/tex]. We use the angle difference identity for sine:
[tex]\[ \sin(45^{\circ} - 30^{\circ}) = \sin 45^{\circ} \cos 30^{\circ} - \cos 45^{\circ} \sin 30^{\circ} \][/tex]

4. Substituting the known values:
[tex]\[ \sin 45^{\circ} = \frac{\sqrt{2}}{2}, \quad \cos 30^{\circ} = \frac{\sqrt{3}}{2}, \quad \cos 45^{\circ} = \frac{\sqrt{2}}{2}, \quad \sin 30^{\circ} = \frac{1}{2} \][/tex]

5. Now, calculate [tex]\(\sin 15^{\circ}\)[/tex]:
[tex]\[ \sin 15^{\circ} = \left(\frac{\sqrt{2}}{2} \cdot \frac{\sqrt{3}}{2}\right) - \left(\frac{\sqrt{2}}{2} \cdot \frac{1}{2}\right) \][/tex]
[tex]\[ \sin 15^{\circ} = \frac{\sqrt{6}}{4} - \frac{\sqrt{2}}{4} \][/tex]
[tex]\[ \sin 15^{\circ} = \frac{\sqrt{6} - \sqrt{2}}{4} \][/tex]

6. Therefore, the exact value of [tex]\(\sin 165^{\circ}\)[/tex] is:
[tex]\[ \sin 165^{\circ} = \frac{\sqrt{6} - \sqrt{2}}{4} \][/tex]

Hence, the correct choice is:
[tex]\[ \boxed{d. \frac{\sqrt{6} - \sqrt{2}}{4}} \][/tex]