# Displacement of a wave

Hi,

I don't understand why I keep getting a negative result...

## Homework Statement

The displacement (in metres) of a wave is given according to

y = 0.26 sin(πt − 3.7πx),

where t is in seconds and x is in metres,

What is the displacement y when t = 38 and x = 13 [m] ?

## The Attempt at a Solution

The wave travels in the +x direction because as time increases so does the displacement, so i'm expecting a +ve result.

$y = 0.26 \sin (\pi 38 - 3.7 \pi 13)$

This keeps giving me $y = -0.1367$ as an answer which surely can't be correct.

I don't know what i'm doing wrong...

Thanks,

BOAS

HallsofIvy