- Given \(\mathbf{ a,x\in\mathbb{R}}\) and \(\mathbf{x\geq 0,a\geq 0}\) . Also \(\mathbf{sin(\sqrt{x+a})=sin(\sqrt{x})}\) . What can you say about a? Justify your answer.

- Given two cubes R and S with integer sides of lengths r and s units respectively . If the difference between volumes of the two cubes is equal to the difference in their surface areas , then prove that r=s.

- For \(\mathbf{n\in\mathbb{N}}\) prove that \(\mathbf{\frac{1}{2}\cdot\frac{3}{4}\cdot\frac{5}{6}\cdots\frac{2n-1}{2n}\leq\frac{1}{\sqrt{2n+1}}}\)

Solution

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- Let \(\mathbf{t_1 < t_2 < t_3 < \cdots < t_{99}}\) be real numbers. Consider a function \(\mathbf{f: \mathbb{R} to \mathbb{R}}\) given by \(\mathbf{f(x)=|x-t_1|+|x-t_2|+…+|x-t_{99}|}\) . Show that f(x) will attain minimum value at \(\mathbf{x=t_{50}}\)

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- Consider a sequence denoted by F_n of non-square numbers . \(\mathbf{F_1=2,F_2=3,F_3=5}\) and so on . Now , if \(\mathbf{m^2\leq F_n<(m+1)^2}\) . Then prove that m is the integer closest to \(\mathbf{\sqrt{n}}\)

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- Let \(\mathbf{f(x)=e^{-x} for all x\geq 0}\) and let g be a function defined as for every integer \(\mathbf{k \ge 0}\), a straight line joining (k,f(k)) and (k+1,f(k+1)) . Find the area between the graphs of f and g.

- If \(\mathbf{a_1, a_2, \cdots, a_7}\) are not necessarily distinct real numbers such that \(\mathbf{1 < a_i < 13}\) for all i, then show that we can choose three of them such that they are the lengths of the sides of a triangle.

- In a triangle ABC , we have a point O on BC . Now show that there exists a line l such that l||AO and l divides the triangle ABC into two halves of equal area.

solution to ques no 2 and 8 of isi bmath 2011