4,589 reputation
11020
bio website jpmccarthymaths.com
location University College Cork, Ireland
age 29
visits member for 2 years, 8 months
seen 17 hours ago

An assistant lecturer at the Cork Institute of Technology. I am also a PhD student of mathematics at University College Cork, Ireland. I hold a BSc and an MSc from UCC. A recent cv, (June 2014) may be found here.

https://jpmccarthymaths.files.wordpress.com/2010/07/resume.pdf


1d
awarded  Good Answer
Jul
18
comment How to get a vector from its length and angle
You see your picture above. Drop a vertical from the 'tip". Now the length of this vertical is the $y$-coordinate. The length of the vector is three as you said. Now, how do you find the sine if an angle?
Jul
18
comment How to get a vector from its length and angle
$x$ and $y$ are what you are looking for - the $x$ and $y$ coordinates.
Jul
18
revised How to get a vector from its length and angle
added 20 characters in body
Jul
18
comment How $+\infty$ is identity element for min operation
Presumably because if you take any numerical input $n$ and ask for $\min(n,\infty)$ you get $n$.
Jul
18
answered How to get a vector from its length and angle
Jul
17
comment Lagrange Interpolation Theorem?
@Ian To be honest as far as I am concerned that goes without saying. Thanks for your help.
Jul
17
comment Lagrange Interpolation Theorem?
@Ian Would I be correct is saying there is a unique polynomial of degree less than or equal to $n$ through $n+1$ points?
Jul
17
revised Lagrange Interpolation Theorem?
deleted 13 characters in body
Jul
17
answered Lagrange Interpolation Theorem?
Jul
16
comment Simplify expression $(x\sqrt{y}- y\sqrt{x})/(x\sqrt{y} + y\sqrt{x})$
...can you not do a little more if you take $xy\neq0$?
Jul
6
awarded  Good Answer
Jul
2
awarded  Curious
Jul
2
comment What is the definition of $G/R$ (the classes of all equivalence classes in G) symbolically?
$\{\bar{a}:a\in G\}$... well I don't really know what you mean by "symbolic explanation".
Jun
30
comment Find the remainder of $\frac{1! +2!+\, \dots\, +95! }{15}$.
@PeterWoolfitt Oh yes I see but didn't know that that was the OP when I wrote this.
Jun
30
answered Find the remainder of $\frac{1! +2!+\, \dots\, +95! }{15}$.
Jun
30
comment Absolute value on the top of a fraction
Good point, well made.
Jun
30
comment Absolute value on the top of a fraction
You can reduce it to two cases by getting rid of the $x=0$ case and including it one of the others; i.e. $|x|=x$ if $x\geq 0$.
Jun
27
comment Prove that $1+\tan^2 x=\sec^2 x$
@mvw Well this is math.stack exchange! Behold my proof that $A$: $1=2$. Multiply both sides by $0$ to get $B$: $0=0$. We know this is true therefore $A$ is true also. See also high school students who start with a true statement $A$ and derive $0=0$ and state "proved". Wrong, wrong, wrong and you shouldn't be defending it with the proper answers above which begin from a true statement.
Jun
27
comment Prove that $1+\tan^2 x=\sec^2 x$
@mvw Yes but the way he has done it, starting with what was to be proved and not deriving a contradiction is not a proof. It is the equivalent of me going into the judge by starting "assume I am innocent". It is sloppy but can be rescued.