Solving a trigonometric equation

Solve on the domain 0° ≦ x ≦ 360°. Use a calculator and round to the nearest degree if unable to use special triangles.

cos x-1 = -cos x

Can anyone give me some pointers on this one? I'm taking grade 12 math through an independent learning course, where I have no access to a teacher, and this question has me completely stuck.

I've solved other trig equations by isolating x and using a special triangle, a calculator, or simply looking at the graph sometimes. However, the right side of the equation has always been a real number in the past, and I'm not sure what to do with this -cos x.

Re: Solving a trigonometric equation

Is it cos (x) - 1 or cos(x-1)?

Re: Solving a trigonometric equation

It is cos x - 1

No brackets written whatsoever

Re: Solving a trigonometric equation

If it is cos x - 1 = -cos x

then 2cos x = 1

cos x = 1/2

x = phi/3 and 5 phi/3

Re: Solving a trigonometric equation

Thanks! I was over-thinking that far too much

Re: Solving a trigonometric equation

Quote:

Originally Posted by

**Lethargic** It is cos x - 1

No brackets written whatsoever

Please learn to use correct notation. The cosine is a **function** and as such it should be written in function notation: .

You would not write for , would you?

Re: Solving a trigonometric equation

Tell that to whomever wrote my textbook

Re: Solving a trigonometric equation

Quote:

Originally Posted by

**coolge** If it is cos x - 1 = -cos x

then 2cos x = 1

cos x = 1/2

x = pi/3 and 5 pi/3

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