There are two similar questions in my homework which need me to solve equations and I have now got stuck on one of them and would like someone to tell me if I have made a mistake in my workings or what I should do next.

Q. Solve 2tan^2 x-7sec+8=0 for 0<x<360

So far I have got:

2tan^2 x-7sec+8=0

2(sin^2 x/cos^2 x)-7cosx+8=0

I am mainly confused because I want to multiply by cos^2 x in order to cancel out the cos^2 x under sin^2 x, but can I do this given that it is all multiplied by 2 i.e. in the brackets?

ALSO: I would be grateful if someone could clarify this for me.

Q. State the values of:

arc sin 0.5 - my answer is 30 degrees

arc tan 1 - my answer is 45 degrees

I ask this because I have no idea what the 'arc' means - does it affect the way I should answer the question as I have never encountered it before.

Many thanks in advance MHF!