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seen May 1 '12 at 7:27

Mar
9
awarded  Popular Question
May
1
comment Proving that if $x$ is not free in $A$, then $(\exists x)(A\to B)\leftrightarrow(A\to(\exists x)(B))$
In axioms 4 and 5, x does not occur free. Sorry, I forgot to mention that.
May
1
revised Proving that if $x$ is not free in $A$, then $(\exists x)(A\to B)\leftrightarrow(A\to(\exists x)(B))$
added 51 characters in body; edited title
May
1
asked Proving that if $x$ is not free in $A$, then $(\exists x)(A\to B)\leftrightarrow(A\to(\exists x)(B))$
Apr
12
revised show that the following is logically valid
edited title
Apr
12
asked show that the following is logically valid
Feb
20
awarded  Student
Feb
20
comment Derive: $(B\to A)\to(\neg A\to\neg B)$
@Gigili I should have added that translating a proposition to its definition is allowed, which I did according to hassan's answer. At one point in my proof, I had to use the first and second axioms as well as modus ponens.
Feb
20
awarded  Scholar
Feb
20
comment Derive: $(B\to A)\to(\neg A\to\neg B)$
Thank you. This helped me solve the problem in less than a minute.
Feb
20
accepted Derive: $(B\to A)\to(\neg A\to\neg B)$
Feb
20
awarded  Editor
Feb
20
revised Derive: $(B\to A)\to(\neg A\to\neg B)$
added 221 characters in body
Feb
20
asked Derive: $(B\to A)\to(\neg A\to\neg B)$
Oct
12
comment Given an angle in radians, how could I calculate a 4x4 rotation matrix about the x, y, z axes?
I need "the rotation matrix (a 4x4 matrix) about the x,y,z axes respectively by the specified angle in radians" Does that make sense? :)
Oct
12
comment Given an angle in radians, how could I calculate a 4x4 rotation matrix about the x, y, z axes?
I am not sure about what I need to do yet, but I think "Perhaps you mean a matrix for an affine transformation, which includes both rotations and translations? That can be written using a 4×4 matrix." is what I need. The matrix at the end of the calculation(s) must be 4x4.
Oct
12
asked Given an angle in radians, how could I calculate a 4x4 rotation matrix about the x, y, z axes?
Sep
22
asked Calculate surface normal of each equilateral triangle in a tetrahedron