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If sin(x-y) = sin x cos y - cos x sin y, then the value of sin⁡(A−B)cos⁡Acos⁡B+sin⁡(B−C)cos⁡Bcos⁡C\frac{\sin(A - B)}{\cos A \cos B} + \frac{\sin(B - C
Question

If sin(x-y) = sin x cos y - cos x sin y, then the value of sin(AB)cosAcosB+sin(BC)cosBcosC\frac{\sin(A - B)}{\cos A \cos B} + \frac{\sin(B - C)}{\cos B \cos C}​is:

A.

sin(CA)cosAcosC\frac{\sin(C - A)}{\cos A \cos C}​​

B.

sin(AC)cosAcosC\frac{\sin(A - C)}{\cos A \cos C}​​

C.

sin(C+A)cosAcosC\frac{\sin(C + A)}{\cos A \cos C}

D.

cos(C+A)cosAcosC\frac{\cos(C + A)}{\cos A \cos C}​​

Correct option is B

Given:
sin(x-y) = sin x cos y - cos x sin y
Formula Used:
sin(AB)cosAcosB+sin(BC)cosBcosC =sinAcosBcosAsinBcosAcosB+sinBcosCcosBsinCcosBcosC =sinAcosBcosAcosBcosAsinBcosAcosB+sinBcosCcosBcosCcosBsinCcosBcosC =sinAcosAsinBcosB+sinBcosBsinCcosC =sinAcosAsinCcosC =sinAcosCcosAsinCcosAcosC =sin(AC)cosAcosC\frac{\sin(A - B)}{\cos A \cos B} + \frac{\sin(B - C)}{\cos B \cos C} \\\ \\= \frac{\sin A \cos B - \cos A \sin B}{\cos A \cos B} + \frac{\sin B \cos C - \cos B \sin C}{\cos B \cos C} \\\ \\= \frac{\sin A \cos B}{\cos A \cos B} - \frac{\cos A \sin B}{\cos A \cos B} + \frac{\sin B \cos C}{\cos B \cos C} - \frac{\cos B \sin C}{\cos B \cos C} \\\ \\= \frac{\sin A}{\cos A} - \frac{\sin B}{\cos B} + \frac{\sin B}{\cos B} - \frac{\sin C}{\cos C} \\\ \\= \frac{\sin A}{\cos A} - \frac{\sin C}{\cos C} \\\ \\= \frac{\sin A \cos C - \cos A \sin C}{\cos A \cos C} \\\ \\= \frac{\sin(A - C)}{\cos A \cos C}​​

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