Thread: Help me solve for x?

1. Help me solve for x?

27 = 20.5sin((2pi/15)x - (pi/2))

I did this:

27/20.5 = sin((2pi/15)x - (pi/2))
arcsin(27/20.5) = (2pi/15)x - (pi/2)
arcsin(27/20.5) + (pi/2) = (2pi/15)x
((arcsin(27/20.5) + (pi/2))/(2pi/15) = x

But when I entered ((arcsin(27/20.5) + (pi/2))/(2pi/15) into a calculator, it said "domain error".

2. Re: Help me solve for x?

Originally Posted by explodingtoenails
27 = 20.5sin((2pi/15)x - (pi/2))
There is no solution to that equation.
$|\sin(x)|\le 1$ but you have there $\frac{27}{20.5}>1$.
So it is impossible.