JUPEBMathematicsTrigonometry

Find the exact value of $\sin 15^\circ$.

A$\dfrac{\sqrt{6} + \sqrt{2}}{4}$
B$\dfrac{\sqrt{6} - \sqrt{2}}{4}$CORRECT
C$\dfrac{1}{4}$
D$\dfrac{\sqrt{3} - 1}{2}$
AI
Toaster Teacher
Why the answer is B, and why the others tempt you.
Write $15^\circ = 45^\circ - 30^\circ$ and use $\sin(A - B) = \sin A\cos B - \cos A\sin B$: $\dfrac{\sqrt{2}}{2}\cdot\dfrac{\sqrt{3}}{2} - \dfrac{\sqrt{2}}{2}\cdot\dfrac{1}{2} = \dfrac{\sqrt{6} - \sqrt{2}}{4}$. The version with a plus sign is $\sin 75^\circ$.
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