Melody

A man on a railroad platform observed that a train passed by the point where he was standing in 10 seconds, and that the same train passed completely through a station, which is 308 meters long, in 24 seconds. How long was the train and how fast was it going? Thanks for help.

I drew a pic to help me think about it.

\(speed=\frac{308m}{14sec}\\=\frac{308*60*60}{14*1000}=79.2km/hour\\~\\ \text{length of train}=\frac{308m}{14sec}\times 10sec=220m\)

Your question does not make sense.

inverse cos is the same as arc cos

use acos  :)

Try watching this

EP is correct :)

but

If sin θ=x and cos θ =y, then x^2=

\(sin^2\theta+cos^2\theta=1\\ \therefore\\ x^2+y^2=1\\ x^2=1-y^2\)

Do this one yourself!

Cos^-1(2/7)

enter it into the calc as       acos(-2/7)

or  press  [2nd]  [acos] (-2/7)

acos(-2/7) = 106.60154959902 degrees

and you can do the other one yourself!

It actually says   asin   but that is short for arc sine which is the same thing as inverse sine :)

Good spotting Electric Pavlov :)

Is that meant to be a question ??