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This Week. Short Course in: Mathematics and Analytic Geometry. Week 8 Complex Numbers. Unreal Quadratic Roots. The roots of quadratic equations: can be found using the quadratic formula : However, if (b 2 < 4ac) then the roots are not real. Unreal Quadratic Roots.
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Short Course in: Mathematics and Analytic Geometry Week 8 Complex Numbers
Unreal Quadratic Roots • The roots of quadratic equations: can be found using the quadratic formula: However, if (b2 < 4ac) then the roots are not real.
Unreal Quadratic Roots • For example, consider roots for the quadratic equation: • The square root of (-1) is undefined in the real number set.
Imaginary Numbers • Terms involving the square root of (-1) form a new numbers, called Imaginary numbers: • The roots for:
Complex Numbers • Quite often imaginary terms appear in sums with real terms; for example: • A complex number is any number that can be expressed in this form: • This implies that real numbers are a subset of the complex numbers.
The Imaginary Powers • The properties of i is as follows: • These powers have a cycle length of 4:
The Complex Plane • Given the distinction between imaginary and real numbers, complex numbers can represent points in a plane:
Complex Numbers in Polar Form • Complex numbers can also be expressed in terms of radius and angle:
Euler’s Formula • Given the power expansions of sin x, cos x and ex: • If x is imaginary:
Complex Number Notations • Just as with vectors, complex numbers can be represented by a single letter (usually z): • Other notations:
Conjugate Pairs • Given a complex number (x + yi), its conjugate pair is (x - yi) and has the following properties:
Euler Rotations • Euler rotations are given by translating the centre of rotation of an object to the origin and applying rotation matrices: • Sometimes called: yaw,roll and pitch.
Gimbals Lock • When rotation matrices are applied in a fixed order (usually pitch, roll and yaw) their operations represent a system of rotation gimbals: • Gimbals lock occurs when any two of these frames coincide on the same plane.
Gimbals Lock • For example, assume we apply rotations in pitch, roll and yaw order, all rotation angles are initially zero and we choose to roll π/2 radians: • Any pitch change is independent of roll and yaw: • However, yaw depends on roll: the result is an anticlockwise pitch rotation, we have lost yaw.
The Quaternion* • A Quaternion can be defined as an extended complex number having the form: • The imaginary parts are as follows:
Quaternion Inverse • Given a quaternion q, the inverse can be found as follows:
Quaternion Rotation • Assume we have a unit vector u and a position vector v and we want to rotate the point described by vector v clockwise about an axis described by u:
Quaternion Rotation • We can define a quaternion q such that: • And θ defines the intended angle of rotation.
Quaternion Rotation • Given quaternion q, a clockwise rotation of θ radian, of a position vector v about the unit vector u, can be defined by the following mapping:
Next Week • SLERP • Curves, Splines and Patches