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naaa00
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Homework Statement
The question is to show that Cos^2(x) + Sin^2(y) = 1 is an equivalence relation.
The Attempt at a Solution
I know that there are three conditions which the equation must satisfy. (reflexivity, symetry, transitivity)
For reflexivity I tried: Cos^2(x) - Cos^2(x) = Sin^2(y) - Sin^2(y) = 0.
For symmetry: ( I don't fully understand this condition) I think that maybe Sin^2(y) + Cos^2(x) = 1 will do. Why? I'm not sure. Any explanation will be very apreciated.
Transitivity: Cos^2(x) + Sin^2(y) = 1, Sin^2(y) + Cos^2(z) = 1, Cos^2(z) + Sin^2(h) = 1.
If I add all o them I'll get Cos^2(x) + Sin^2(y) + Sin^2(y) + Cos^2(z) + Cos^2(z) + Sin^2(h) = 1 + 1 + 1
I was tempted to say that Sin^2(y) = Sin^2(z) = Sin^2(h), and that cos^2(x) = cos^2(z) (my thought was: "since they are supposed to be equivalent...") and rewrite it as:
3Cos^2(x) + 3Sin^2(h) = 3 (and then I divide it by 3)
Cos^2(x) + Sin^2(h) = 1.
I think my methods are wrong.
Any help will be very appreciated.