If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# Modeling with sinusoidal functions: phase shift

## Problem

The length of the day in Lagos, Nigeria (in minutes), t days since the beginning of the year can be estimated by this formula:
L, left parenthesis, t, right parenthesis, equals, 727, plus, 22, sine, left parenthesis, start fraction, 2, pi, left parenthesis, t, minus, 80, point, 75, right parenthesis, divided by, 365, end fraction, right parenthesis.
When is the longest day of the year? Give an exact answer.
days since the beginning of the year
Stuck?
Stuck?