Paper 2, Section I,

Metric and Topological Spaces | Part IB, 2012

For each case below, determine whether the given metrics d1d_{1} and d2d_{2} induce the same topology on XX. Justify your answers.

 (i) X=R2,d1((x1,y1),(x2,y2))=sup{x1x2,y1y2}d2((x1,y1),(x2,y2))=x1x2+y1y2. (ii) X=C[0,1],d1(f,g)=supt[0,1]f(t)g(t)d2(f,g)=01f(t)g(t)dt.\begin{gathered} \text { (i) } X=\mathbb{R}^{2}, d_{1}\left(\left(x_{1}, y_{1}\right),\left(x_{2}, y_{2}\right)\right)=\sup \left\{\left|x_{1}-x_{2}\right|,\left|y_{1}-y_{2}\right|\right\} \\ d_{2}\left(\left(x_{1}, y_{1}\right),\left(x_{2}, y_{2}\right)\right)=\left|x_{1}-x_{2}\right|+\left|y_{1}-y_{2}\right| . \\ \text { (ii) } X=C[0,1], d_{1}(f, g)=\sup _{t \in[0,1]}|f(t)-g(t)| \\ d_{2}(f, g)=\int_{0}^{1}|f(t)-g(t)| d t . \end{gathered}

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