Here's the question you clicked on:
lolroark
a missile is launched with an initial speed of 421.1 m/sec. after 13.77 seconds, it is at its highest point. Q: what was its initial launch angle above the horizon?
i think i solved it by myself but not sure. is it 13.77-9.8/421.1?
time to reach max height is given by \[t=\frac{usin\theta}{g}\]