Calculating arc length of trajectory

Today I continued the course "Physics of the Everyday" and in Quiz 9 of On the Field there was a question about the average speed of a baseball. We know that the ball flies to someone who is 127.5 feet away in 1.25 seconds and the task was to estimate what the actual average speed of the ball could be.

I do understand the estimation in the quiz, but in the answer it is stated that the hard way to answer the question would be to calculate the actual arc length d. I've thought about it for quite a while, but cannot figure out how to do that. Any help is appreciated. ^^

#Mechanics

Easy Math Editor

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Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$