Question 81

2sinA sinB is equal to

Solution

Expression : 2sinA sinB

= $$sinAsinB + sinAsinB$$

Adding and subtracting $$(cosAcosB)$$

= $$(cosAcosB + sinAsinB) + (-cosAsinB + sinAcosB)$$

= $$(cosAcosB + sinAsinB) - (cosAcosB - sinAsinB)$$

= $$cos(A-B) - cos(A+B)$$

=> Ans - (B)

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