# Thread: Trigonometric equations help (again!)

1. ## Trigonometric equations help (again!)

Prior knowledge tells me that to get maximum I would turn sin() into its maximum value (1), making the maximum y=18-5*1 = 13. But this isn't correct. My calculator tells me that's the minimum, and that 18+5 would give the maximum.
How would I find that without a calculator?

2. You are trying to maximize the value of 18 - 5 sin (junk). The greatest value for 18 - 5 sin (junk) occurs when the sine function is at a minimum, because its coefficient is negative. This is when sin(junk) = -1, which nets you 23 from your function.

3. Oh. So because we have a negative sin, because of the negative 5, it's the minimum value of sin we're after?
That's something I didn't know. Thanks again! You're my hero.