precalc help

[vbeierschmitt]

cosx-5=3cosx+6

 

[Deleted member 4993]

Check your post for accuracy - then show your work to get proper help...

 

[vbeierschmitt]

thats the problem from the book. Dont no how to get started solving

 

[mmm4444bot]

cosx-5=3cosx+6

Your book should show grouping symbols around function inputs.

If it does not, then we must assume that the angle (i.e., the input to each cosine function) is simply x.

cos(x) - 5 = 3*cos(x) + 6

This equation has no Real solution.

To see why, do the algebra:

(1) Subtract cos(x) from both sides

(2) Subtract 6 from both sides

(3) Simplify

You should arrive at:

cos(x) = -11/2

This equation has no Real solution because -11/2 is smaller than -1 and the range of the cosine function is [1, -1].

If I wrote anything that you do not understand, please ask a specific question. Cheers! :cool: