4-gon with two opposite sides congruent and two opposite angles congruent: necessarily a parallelogram?
45913
If a quadrilateral has a pair of equal opposite sides, and a pair of equal opposite angles, then is it necessarily a parallelogram?
126885
canonical representation of three skew lines in $\mathbb{P}^3$
120912
Can two Pythagorean triples have the same product?
83679
Writing a non symmetrical function as an even or odd function
71245
$2 \times 2 $ Orthogonal Group
136644
Cyclic Quadrilateral Problems
81975
Sequence of triangles with exponentiated sides
158727
Leg bisectors in a trapezoid and angle equality
117431
Are the proofs for the properties of parallel lines, and that a triangle has 180 degrees, inherently tautological?
79808
Prove the representation of complex numbers is parallelogram
147410
ArcTan(2) a rational multiple of $\pi$?
95108
Alternative form of ArcSin[Sin[x]]
8094
X, Y, Z — horizontal, vertical and ...?
52161
Square bracket notation for anti-symmetric part of a tensor
55259
ArcTan[z] and ArcTan[x,y], Restriction and Conversion
64243
How to find a 4D vector perpendicular to 3 other 4D vectors?
74574
Are all equiangular odd polygons also equilateral?