Answer
$y=5 \sin 4 x$
Work Step by Step
As we can see from the given picture that the amplitude $A=5$
Thus, the time period $P$ will be: $P=\dfrac{\pi}{2}$
or,
$\dfrac{2\pi}{k}=\dfrac{\pi}{2}$
This gives : $k=4$
But there is no horizontal shift, this means that $B=0$
Hence, our function is: $y=5 \sin 4 x$
