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English: Symbol used to denote first-angle projection in a manner independent of written language. Date: 5 April 2013: ... First Angle Projection: Width: 200: Height: 100
The concept of projection in mathematics is a very old one, and most likely has its roots in the phenomenon of the shadows cast by real-world objects on the ground. This rudimentary idea was refined and abstracted, first in a geometric context and later in other branches of mathematics. Over time different versions of the concept developed, but ...
For example, one sphere that is described in Cartesian coordinates with the equation x 2 + y 2 + z 2 = c 2 can be described in spherical coordinates by the simple equation r = c. (In this system—shown here in the mathematics convention—the sphere is adapted as a unit sphere, where the radius is set to unity and then can generally be ignored ...
The scalar projection is defined as [2] = ‖ ‖ = ^ where the operator ⋅ denotes a dot product, ‖a‖ is the length of a, and θ is the angle between a and b. The scalar projection is equal in absolute value to the length of the vector projection, with a minus sign if the direction of the projection is opposite to the direction of b ...
A square matrix is called a projection matrix if it is equal to its square, i.e. if =. [2]: p. 38 A square matrix is called an orthogonal projection matrix if = = for a real matrix, and respectively = = for a complex matrix, where denotes the transpose of and denotes the adjoint or Hermitian transpose of .
For instance, the target orientation can be reached as follows (note the reversed order of Euler angle application): The XYZ system rotates about the z axis by γ. The X axis is now at angle γ with respect to the x axis. The XYZ system rotates again, but this time about the x axis by β. The Z axis is now at angle β with respect to the z axis.
PGA allows projection, meet, and angle formulas to be derived from (,,) - with a very minor extension to the algebra it is also possible to derive distances and joins. PGA is a widely used system that combines geometric algebra with homogeneous representations in geometry, but there exist several other such systems.
The angle θ which appears in the eigenvalue expression corresponds to the angle of the Euler axis and angle representation. The eigenvector corresponding to the eigenvalue of 1 is the accompanying Euler axis, since the axis is the only (nonzero) vector which remains unchanged by left-multiplying (rotating) it with the rotation matrix.