67,948 reputation
143129
bio website math.ethz.ch/~blatter
location Switzerland
age 79
visits member for 4 years, 3 months
seen 8 hours ago

9h
revised function of three variable is even than $f(a,b,c)=f(|a|,|b|,|c|)$
deleted 33 characters in body
9h
answered Roll 3 dice. Calculate the size of the event where the largest value of d1, d2, d3 is 6.
10h
answered function of three variable is even than $f(a,b,c)=f(|a|,|b|,|c|)$
12h
revised How to define the complex square root $ \sqrt{z} $?
deleted 28 characters in body
13h
reviewed Approve suggested edit on German exercise - about “Normale im Wendepunkt”
14h
comment $Ax=b$ what does solving it mean?
@MathIsHardNoItsNot: See my edit.
14h
revised $Ax=b$ what does solving it mean?
added 159 characters in body
15h
answered $Ax=b$ what does solving it mean?
17h
comment Linear algebra and geometric insight: a rigorous approach to vector spaces, matrices, and linear applications
There are tons of textbooks doing exactly this, the mother of them all being Halmos' Finite dimensional vector spaces (1958).
17h
answered How do you generally prove that the sum of a right triangle's hypotenuse and it's base have a common factor with the perpendicular side?
18h
answered How many words can be written with $aabbbccdd$ such that no two equal letters are adjacent?
1d
comment Find the indicial equation
Introducing a new independent variable $t$ such that $x=e^t$ transforms a given Euler differential equation into a differential equation with constant coefficients. It follows that the "algebraic theories" of these two types of differential equations are "isomorphic". The characteristic polynomial of constant coefficient equations appears as "indicial polynomial" in the case of Euler differential equations.
1d
revised conformal mapping, regions of the complex plane marked +/-, find the function f,
added 86 characters in body
1d
answered How to prove a function has no local minima.?
1d
answered New proof about normal matrix is diagonalizable.
1d
revised Find the indicial equation
added 22 characters in body
1d
comment Maximizing cross sectional area of trapezoid
Your $A(b,c,h)$ is wrong: You need $\sqrt{c^2-h^2}$ instead of $c^2-h^2$. Always check the dimensions in geometric calculations!
1d
revised General form of a Möbius transformation sending two points to two points and a circle to another.
deleted 17 characters in body
2d
answered General form of a Möbius transformation sending two points to two points and a circle to another.
2d
comment When is a vector field on a manifold restricted to a submanifold $X$ a vector field on $X$?
To put it simply: The condition is that $V(p)\in T_p(X)$ for all $p\in X$.