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Arnaldo
  • Member for 7 years, 5 months
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16 votes
1 answer
208 views

Prove that $0<\det(A) \le 1$

15 votes
4 answers
2k views

Proving that $\det(A) \ne 0$ if $a_{i,i} = 0$ and $a_{i,j} = \pm 1$ for $i \neq j$

7 votes
1 answer
415 views

Solve $2\cdot \sin x \cdot \sin (50°+2x)=\sin (50°)$

5 votes
2 answers
137 views

$f\circ f\circ f(x)=x^9$ then $f$ is increasing

4 votes
2 answers
210 views

Solve $(2^x+3^x+5^x)^3=160^x$

4 votes
1 answer
102 views

Finding $f$ such that $f(x)+f(y)=f\left(\frac{x+y}{1-xy}\right)$

3 votes
0 answers
36 views

Similarity of real-valued functions

2 votes
2 answers
57 views

Calculate $\lim_{x\to 0}\left[\left[\log \left(1+\frac{1}{cx}\right)\right]^b-\left[\log \left(1+\frac{1}{x}\right)\right]^b\right]$

2 votes
2 answers
171 views

Periodic Function and change of scale

1 vote
2 answers
48 views

$f$ is continuous and $f(0)\ge f(x)$, for all $x\in [0,\delta]$

1 vote
2 answers
4k views

Variance of $X^2$ if $X \sim \mathcal{N}(0,1)$?

1 vote
2 answers
190 views

Power-like functional equation

1 vote
4 answers
336 views

$2f(x)=f(y) \Rightarrow 2f(tx)=f(ty)$

1 vote
1 answer
128 views

Quadrilateral inscribed in a circle

1 vote
1 answer
129 views

Evaluate $\int_{0}^{x} f(t)dt$

1 vote
1 answer
95 views

Real solutions of $x=\sqrt{2+\sqrt{2-\sqrt{2+x}}}$ [duplicate]

1 vote
2 answers
794 views

Prove that we can construct a line segment with the length $\sqrt{n}$.

0 votes
2 answers
1k views

Rational approximation for irrational number

0 votes
1 answer
35 views

Find function $f(ax+b)+c \le x \le f(x+c)+b$