Friday, December 3, 2010

Evaluate the limit of expression 4cosx-6sin^2x+3tan^2x. x-->x0 , x0=60 degrees

To evaluate the limit, we'll have to substitute x by the
value of x0, in the given expression.


lim
(4cosx-6sin^2x+3tan^2x) = 4cos 60 - 6*(sin 60)^2 + 3*(tan
60)^2


cos 60 = 1/2


sin 60 =
sqrt3/2


We'll raise to square both
sides:


(sin 60)^2 =
(sqrt3/2)^2


(sin 60)^2 =
3/4


tan 60 = sqrt 3


We'll
raise to square both sides:


(tan 60)^2 =
3


We'll substitute the values of the functions in the
expresison above:


lim (4cosx-6sin^2x+3tan^2x) = 4(1/2) -
6*(3/4) + 3*(3)


lim (4cosx-6sin^2x+3tan^2x) = 2 - 9/2 +
9


lim (4cosx-6sin^2x+3tan^2x) = (4 - 9 +
18)/2


lim (4cosx-6sin^2x+3tan^2x) = 13/2, for
x-> 60 degrees

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