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Jan
30
answered Angle vector in polar system represented by Cartesian vector
Jan
29
comment Equation of a circle whose radius and tangent is given
$y= m x$ will never be tangent to a centered circle. A tangent line will have all its points outside the circle and the origin is inside the circle while belonging to the line also. Please rephrase the question.
Jan
29
answered Relationship between factorial and derivatives
Jan
24
comment Modelling free fall with Euler
@NobleMushtak This would yield more accurate results, but it won't be Euler's method. The OP has to decide.
Jan
23
comment Moment of Inertia around z axis
First you find the center of mass from the origin and then you calculate the MMOI about the origin. lastly you use the parallel axis theorem to transfer the MMOI to the center of mass.
Jan
23
answered Rotating a 3 coordinate point
Jan
18
answered Understanding what a plane is in $\mathbb R^3$
Jan
17
comment Finding a suitable matrix to solve equation
@Peter also scalar multiples of this matrix are solutions.
Jan
17
comment Finding a suitable matrix to solve equation
Solutions to the first equation are: Try $T = \lambda \begin{vmatrix} \cos\theta & \sin\theta \\ \sin\theta & \cos\theta \end{vmatrix}$ or $T = \mu \begin{vmatrix} -\sin\theta & \cos\theta \\ \cos\theta & -\sin\theta \end{vmatrix}$
Jan
16
revised Find the eccentricity of a conic
added 342 characters in body
Jan
16
comment Find the eccentricity of a conic
@robjohn I disagree. Look at my edit, which shows the derivation of eccentricity for a conic more rigorously. Where did you get your eccentricity values from. Note also that the second equation above is equivalent to $-75 x^2 + 26 y^2 -1 =0$ which should different eccentricity not because $C$ is different but because what is considered a major and a minor radius is different (interchanged).
Jan
16
revised Find the eccentricity of a conic
added 342 characters in body
Jan
16
comment Find the eccentricity of a conic
it is not used. I just included it here for completeness. $C$ is like a size/scale parameter, and $A$, $B$ dictate the shape.
Jan
15
revised Find the eccentricity of a conic
added 189 characters in body
Jan
15
answered Find the eccentricity of a conic
Jan
14
comment Notation of the second derivative - Where does the d go?
A value can be infinitesimally small without being zero, the same way the Dirac function can be infinite but evaluate to a finite value over an integral. So the result of ${\rm d}(A)$ exists in $\Bbb R$ although undefined. I think you imply that ${\rm d}x \equiv 0$ whereas I imply that ${\rm d}x \neq 0$
Jan
14
comment Notation of the second derivative - Where does the d go?
Ok, I added the word "infinitesimally" to the answer. Happy now? The point of the answer is to view the ${\rm d}(\square)$ as an operator.
Jan
14
revised Notation of the second derivative - Where does the d go?
added 19 characters in body
Jan
14
comment Notation of the second derivative - Where does the d go?
Actually it is $$ \frac{{\rm d}A}{{\rm d}x} = \lim_{h\rightarrow 0} \frac{ \left(A(x+h) - A(x)\right)}{\left( (x+h)-x \right)} $$ This is the definition of a derivative (en.wikipedia.org/wiki/Derivative).
Jan
14
answered Notation of the second derivative - Where does the d go?