2sin[(C+D)/2].cos[(C-D)/2] is equal to
A) sinC - sinD B) cosC + cosD C) cosC - cosD D) sinC + sinD
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Step-by-step explanation:
Step-by-step explanation:
w/k,sin(A+B)+sin(A-B)=2sinAcosB
let,A+B=C ......(i)
A-B=D......(ii)
(i)+(ii)2A=C+D
A=C+D/2
(i)-(ii)2B=C-D
B=C-D/2
so,sin(A+B)+sin(A-B)=2sinAcosB
sinC+sinD=2sin(C+D/2)cos(C-D/2)
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B) cosC + cosD
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