Answer
The partner found $\sin 4^{o}$, not $\sin 4.$
(He did not set his calculator to radians).
Work Step by Step
$\theta=4$ rad terminates in quadrant III
$(\displaystyle \pi < 4 < \frac{3\pi}{2})$, where sine is negative.
The positive result of the partner is positive,
implying quadrant I or II,
so his "4" is $4^{o}$.
The partner found $\sin 4^{o}$, not $\sin 4.$
(He did not set his calculator to radians).
