Metric space Triangular inequalities

beetle2
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Homework Statement



let <br /> (X,\sigma) be a metric space. xyz \in Rshow that
<br /> \mid \sigma(x,z)-\sigma(y,z) \mid \leq \sigma(x,y)

Homework Equations





The Attempt at a Solution



\mid \sigma(x,z)-\sigma(y,z) \mid \leq \sigma(x,y)=\mid \sigma(x,y) \mid = \mid\sigma<br /> (z,x) + \sigma(z,y) \mid

\leq \mid\sigma<br /> (x,z)\mid + \mid \sigma(y,z) \mid


Does that look alright?
 
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For real numbers a and b, |a+b| <br /> <br /> \leq <br /> |a| + |b|.
Thus, |a| + |b|.= |(a-c) + (c-b)| <br /> <br /> \leq <br /> |a-c| + |c-b|
 
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