help with inverse trigonometric functions

I am stuck on these 2 problems and was wondering if someone could work them out for me?

http://i232.photobucket.com/albums/e...Untitled-1.png

what have you tried ?

Are you aware of this tool?

this is a brilliant tool thank you very much! But i do have one problem. For this problem sin(arccos 2/5 - arctan5) - Wolfram|Alpha I need exact form and it gives it ot me in decimal. What can I do?

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Originally Posted by wonderd

this is a brilliant tool thank you very much! But i do have one problem. For this problem sin(arccos 2/5 - arctan5) - Wolfram|Alpha I need exact form and it gives it ot me in decimal. What can I do?

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work it out by hand using the difference identity for sine and some right triangle trig.

would someone be willing to work it out for me?

What does equal? What is the inverse cosine of that?