Natural display calculator seriously stressing me out. can someone help me please?

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all i want to do is calculate sin a = 3/4
in my old calculator, i would do 3 dived four. get an answer. then press inverse, and sin and hit = and get the bloody angle. but this natural display thing wants to right it out the way it is in the book. fine, let it do that. but it wont give me an answer.
also, i was trying to find the square of 200 , (yes i know its 4000, but i want to make sure the calculator and i are working properly, ) and it gives me 0000
wtf
whsmith says its not possible to buy the 'old fashioned' ones any more.
please help me, before i tear all my hair out.

Er, the square of 200 is 40,000.

I don't have a new fangled calculator in front of me, but it is not that hard - something like 3 [div] 4 = [inv] [sin] [ans] - the point is that the operator keys generally come before the arguments, as they would if you were writing it out, and the [ANS] key inserts the last answer.

Or just use an online scientific calculator - find one with google.

Why do you want to know that angle anyway?

thank you.
yes, i missed out the extra zero when typing this post.
trying to do some vector problems, and this is one of the sums. i've managed to work out that part of the screen onthis calculater has stopped working, whichis why it doesnt show anythingthere, and the nummber came up as 0000.
the new way of doing it may be more natural, but as someone who learnt the 'unnatural way' and did all her exams with such a calculator, i am finding this harder to use.