1. ## trigonometric function

i know how to work out the first two parts to the question the period is 12 and the range is [50,20] and a=15 and b=30 but i dont know how to do the last part
i tried to work out the following 15cos30t+50<25 but when i try to work this out you cant get the cos inverse of 5/3

2. ## Re: trigonometric function

The mean value is 50 and the amplitude is 15, thus the range of the function is [35, 65]. I think that should prove that there is not any value of t which satisfies your inequality.

3. ## Re: trigonometric function

i tried to work out the following 15cos30t+50<25
If $t$ is in degrees (should be radians imho), then your inequality is

$15\cos(30t) + \color{red}{35} < 25$

solving this inequality yields $4.4 < t < 7.6$ in the first period of 12 months

4. ## Re: trigonometric function

does c not stands for the constant where it cuts the y axis. from the diagram it cuts it at 50

5. ## Re: trigonometric function

Originally Posted by markosheehan
does c not stands for the constant where it cuts the y axis. from the diagram it cuts it at 50
No, "c" represents the midline of the curve ... see attached graphs.

Do you not graph your equations to check your results? Maybe you should start.

6. ## Re: trigonometric function

The answer is 4 at the back of the book so they must of rounded of and I do not graph my questions as I do not know how to.

7. ## Re: trigonometric function

Originally Posted by markosheehan
I do not graph my questions as I do not know how to.
... then maybe you should learn how.