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Apr
10
comment Understanding the definition of a set with $C^k$ boundary and of the outward pointing normal vector field
How would you define the normal vector at the corners of the square? Think about what it means to be the normal vector there... And why a lack of $C^1$ is a problem...
Apr
10
comment Understanding the definition of a set with $C^k$ boundary and of the outward pointing normal vector field
How about $U$ the interior of a square? Then the boundary of $U$ is continuous, but not smooth ($C^1$) at the corners.
Apr
8
awarded  Enlightened
Apr
8
awarded  Nice Answer
Apr
3
awarded  Nice Answer
Apr
3
comment Find Transformation Matrix $T$ relative to new bases such that $T$ is in diagonal form
This is the only approach I know of off the top of my head.
Apr
1
revised Find Transformation Matrix $T$ relative to new bases such that $T$ is in diagonal form
added 8 characters in body
Apr
1
answered Find Transformation Matrix $T$ relative to new bases such that $T$ is in diagonal form
Feb
3
awarded  Fanatic
Jan
21
reviewed Approve Inequality $(n!)^2\le \left[\frac{(n+1)(n+2)}{6}\right]^n$
Jan
21
reviewed Approve Point of intersection closest to the origin
Jan
21
reviewed Approve How to solve the improper integral $\int_{-\infty}^{\infty} \frac{x^2}{x^6+9}dx$ (possible trig substitution)
Jan
21
reviewed Approve Differential Equation $y'+y\cdot\frac{1}{1+t^2}=1-y\cdot\frac{t^3}{1+t^4}$
Jan
21
reviewed Reject How does constant affect the limit
Jan
21
reviewed Approve Finding the volume of revolution using the method of shells
Jan
19
comment Why is it that while taking the inverse matrix a Wronskian pops up in this solution?
Glad to help. The more you learn/farther you go in mathematics you will see more and more connections between all the things you've already done.
Jan
19
answered Why is it that while taking the inverse matrix a Wronskian pops up in this solution?
Jan
8
reviewed No Action Needed Circle tangent to two other circles
Jan
8
reviewed No Action Needed Calculating area of complex ploygons (odd shapes)
Jan
8
reviewed No Action Needed Deduction Theorem and Closed Formulas