# Question about functions and a identity Question

• Sep 8th 2008, 09:26 PM
fishguts
Question about functions and a identity Question
I have two quick questions about basic trig.My first question is asking to find period, amplitude, and phase shift of a function written as

f(x) = -cos(pi(x - 0.1))

Can i write the function as

f(x) = -cos(pi x - 0.1)?

Also I was asked to find the values of x between [0, 2pi] of the following equation

2sin^2 = 1

When i solve this equation I get

sinx = 1/ root 2

There is no special angle or this solution so would I use a decimal approximation?

Thanks for any help
• Sep 8th 2008, 09:38 PM
mr fantastic
Quote:

Originally Posted by fishguts
I have two quick questions about basic trig.My first question is asking to find period, amplitude, and phase shift of a function written as

f(x) = -cos(pi(x - 0.1))

Can i write the function as

f(x) = -cos(pi x - 0.1)? Mr F says: No. $\displaystyle {\color{red}f(x) = - \cos (\pi x - 0.1 \pi)}$.

Also I was asked to find the values of x between [0, 2pi] of the following equation

2sin^2 = 1

When i solve this equation I get

sinx = 1/ root 2 Mr F says: $\displaystyle {\color{red}\sin x = \pm \frac{1}{\sqrt{2}} = \pm \frac{\sqrt{2}}{2}}$.

There is no special angle Mr F says: Yes there is.

or this solution so would I use a decimal approximation? Mr F says: No. See above.

Thanks for any help

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• Sep 8th 2008, 10:03 PM
fishguts
Quote:

Originally Posted by mr fantastic
..

Thanks man for the first one I forgot to rationalize the denominator that why I was not getting that one, and the second problem I was not too sure. And also sorry about the syntax