5,873 reputation
31751
bio website ophirgame.com
location United States
age 72
visits member for 3 years, 6 months
seen Aug 24 at 22:58

(update) - I'm having a board game published! We'd appreciate your support on Facebook or on Twitter, as we prepare for a Kickstarter campaign in early 2014.


I hereby commit to contributing to this site without any rudeness, sarcasm, accusation, or any other unloving speech.


Nov
2
answered By definition, how is a prime number represented?
Nov
1
comment It is valid that $A \subset B$. Prove that $A \cap B = A$
Do you know that $A \cap A = A$?
Nov
1
revised Solving 4th degree polynomials
deleted 1 characters in body
Nov
1
answered How to isolate y?
Nov
1
comment Logic Riddle - Multiple Choice
In 4), the innermost shape becomes the outermost. There is an alternation of black/white, and an alternation of which way the triangle is pointing. So I'd go with "B"
Nov
1
comment Logic Riddle - Multiple Choice
The first is E. You move from one picture to the next by rotating one stick a quarter turn to the left.
Nov
1
comment Complex number: Roots
Let $z = x + iy $ in the second one and use the definition of absolute value.
Nov
1
comment Logial Entailment vs. Material Conditional: binding free variables?
Also, en.wikipedia.org/wiki/Vacuous_truth
Nov
1
comment Area under the curve
The integral gives signed area. Also, what's the function for the ellipse?
Nov
1
comment If $f(x)=\int_0^x x^2 \sin {t^2}~dt $, find $f'(x)$.
Yes! Good luck to you.
Nov
1
comment Logarithmic function
@user: you might consider editing your question to include the above comment. That kind of thought/effort is highly sought after!
Nov
1
comment If $f(x)=\int_0^x x^2 \sin {t^2}~dt $, find $f'(x)$.
You really should think about the Bonus question though! It requires the chain rule...
Nov
1
comment Determinant from matrix entirely composed of variables
Do not underestimate the power of laziness! :)
Nov
1
comment If $f(x)=\int_0^x x^2 \sin {t^2}~dt $, find $f'(x)$.
Almost. Your first term should be $x^2 \sin (x^2)$.
Nov
1
comment Determinant from matrix entirely composed of variables
No love for theory? What if it's a $5 \times 5$ matrix ?? ;)
Nov
1
comment Determinant from matrix entirely composed of variables
Sure, but there are theoretical reasons. See property 7
Nov
1
comment If $f(x)=\int_0^x x^2 \sin {t^2}~dt $, find $f'(x)$.
Since the integral is with respect to a different variable, $t$, you can treat the $x^2$ as a constant and write the integral as $$x^2 \cdot \int_0^x sin(t^2)dt$$
Nov
1
answered Determinant from matrix entirely composed of variables
Nov
1
answered If $f(x)=\int_0^x x^2 \sin {t^2}~dt $, find $f'(x)$.
Nov
1
comment If $f(x)=\int_0^x x^2 \sin {t^2}~dt $, find $f'(x)$.
Pull out the $x^2$, then use the product rule and the fundamental theorem of calculus.