contestada

Which of the following expression expressions is equivalent to cos3x/sinxcosx?
A.) cscxcos2x-secxsin2x
B.) secxcos2x-cscxsin2x
C.) secxcosx-cscxsinx
D.) cscxcosx-secxsinx

Respuesta :

calculista
we have
cos3x/(sinxcosx)

we know that
cos(3x) can be written as
cos(2x +x)=[cos2x*sinx-sin2x*cosx]
Using this value of cos(3x) in given equation
[cos2x*sinx-sin2x*cosx]/(sinxcosx)

[cos2x*sinx]/(sinxcosx)-[sin2x*cosx]/(sinxcosx)
[cos2x]/(cosx)-[sin2x]/(sinx)---------> secx*cos2x-csecx*sin2x

the answer is the option B.) secxcos2x-cscxsin2x 

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