The value of sin 780^{circ} sin 480^{circ} + | vedclass

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Question

(A) We use the reduction formulas for trigonometric functions:$\sin 780^{\circ} = \sin(2 	imes 360^{\circ} + 60^{\circ}) = \sin 60^{\circ} = \frac{\s

Vedclass · Accepted Answer

$\frac{1}{2}$

Vedclass · Answer

(A) We use the reduction formulas for trigonometric functions:$\sin 780^{\circ} = \sin(2 	imes 360^{\circ} + 60^{\circ}) = \sin 60^{\circ} = \frac{\sqrt{3}}{2}$$\sin 480^{\circ} = \sin(360^{\circ} + 120^{\circ}) = \sin 120^{\circ} = \sin(180^{\circ} - 60^{\circ}) = \sin 60^{\circ} = \frac{\sqrt{3}}{2}$$\cos 240^{\circ} = \cos(180^{\circ} + 60^{\circ}) = -\cos 60^{\circ} = -\frac{1}{2}$$\cos 300^{\circ} = \cos(360^{\circ} - 60^{\circ}) = \cos 60^{\circ} = \frac{1}{2}$Substituting these values into the expression:$\sin 780^{\circ} \sin 480^{\circ} + \cos 240^{\circ} \cos 300^{\circ} = \left(\frac{\sqrt{3}}{2}ight) \left(\frac{\sqrt{3}}{2}ight) + \left(-\frac{1}{2}ight) \left(\frac{1}{2}ight)$$= \frac{3}{4} - \frac{1}{4} = \frac{2}{4} = \frac{1}{2}$

The value of $\sin 780^{\circ} \sin 480^{\circ} + \cos 240^{\circ} \cos 300^{\circ} = $

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