Maths WorkshopMaths problems with full solutions

Complex numbers

54 problems · Complex plane, De Moivre's formula, roots of unity and complex functions.

Ex.190A power of 1 + i
#complex numbers
Complex numbers
L1
L1
Ex.220Basic operations on complex numbers
#complex numbers #addition #multiplication #conjugate
Complex numbers
High school
High school
Ex.221The equation $z=\bar z$
#conjugate #real axis #equation
Complex numbers
High school
High school
Ex.222Modulus via the conjugate
#modulus #conjugate #formula
Complex numbers
High school
High school
Ex.421Midpoint and centroid in the complex plane
#midpoint #centroid #complex plane
Complex numbers
High school
High school
Ex.422Argument of a quotient
#argument #quotient #computation
Complex numbers
L1
L1
Ex.423Properties of the conjugate
#conjugate #properties #modulus
Complex numbers
High school
High school
Ex.424The cube roots of unity
#cube roots #unity #cyclic
Complex numbers
High school
High school
Ex.425De Moivre's formula
#De Moivre #powers #trigonometric form
Complex numbers
High school
High school
Ex.426Exponential form
#exponential form #Euler #polar
Complex numbers
High school
High school
Ex.427Geometric interpretation of operations
#complex plane #geometric interpretation #translation
Complex numbers
High school
High school
Ex.428Rotation via multiplication
#rotation #multiplication #geometric
Complex numbers
High school
High school
Ex.429Modulus and argument
#modulus #argument #trigonometric form
Complex numbers
High school
High school
Ex.430Modulus of a product
#modulus #product #quotient
Complex numbers
L1
L1
Ex.431A quadratic with complex roots
#quadratic #complex roots #conjugate roots
Complex numbers
High school
High school
Ex.432Product of complex numbers in trigonometric form
#trigonometric form #product #quotient
Complex numbers
High school
High school
Ex.433Solving $z^3=1$
#cube roots of unity #algebraic solution
Complex numbers
High school
High school
Ex.825Argument of a product
#argument #product #additive property
Complex numbers
L1
L1
Ex.826Conjugate roots of real polynomials
#conjugate roots #real polynomials #complex
Complex numbers
High school
High school
Ex.827Cube roots of a complex number
#cube roots #complex #De Moivre
Complex numbers
L1
L1
Ex.828Linearizing powers of cosine
#De Moivre #linearization #cos
Complex numbers
High school
High school
Ex.829De Moivre's formula by induction
#De Moivre #induction #proof
Complex numbers
L1
L1
Ex.830A circle given by a modulus equation
#modulus #circle #locus
Complex numbers
L1
L1
Ex.831The modulus equation $|z-a|=|z-b|$
#perpendicular bisector #modulus #locus
Complex numbers
L1
L1
Ex.832Triangle inequality for complex numbers
#triangle inequality #modulus #complex
Complex numbers
High school
High school
Ex.833A locus defined by a modulus equation
#locus #modulus #geometric interpretation
Complex numbers
L1
L1
Ex.834The $n$-th roots of unity
#roots of unity #De Moivre #cyclic group
Complex numbers
L1
L1
Ex.835The perpendicular bisector
#locus #perpendicular bisector #modulus
Complex numbers
L1
L1
Ex.836Square roots of a complex number
#square roots #complex #algebraic method
Complex numbers
L1
L1
Ex.837Computing roots with De Moivre
#nth roots #De Moivre #formula
Complex numbers
L1
L1
Ex.838Sum of the $n$-th roots of unity
#roots of unity #sum #geometric series
Complex numbers
L1
L1
Ex.839Linearizing $\sin^4\theta$
#linearization #sin #De Moivre
Complex numbers
L1
L1
Ex.1227The sum of 1/(1 − ω^k)
#roots of unity #symmetry #complex numbers #pairing
Complex numbers
Olympiad
Olympiad
Ex.1229Three unit complex numbers with zero sum
#complex numbers #unit circle #equilateral triangle #conjugate trick
Complex numbers
Olympiad
Olympiad
Ex.1294Three complex numbers of modulus one
#complex numbers #unit circle #conjugation #equilateral triangle
Complex numbers
Olympiad
Olympiad
Ex.1305Sums over roots of unity from a logarithmic derivative
#roots of unity #logarithmic derivative #complex numbers #symmetry
Complex numbers
Olympiad
Olympiad
Ex.1567An inequality involving arguments
#argument #inequality #complex
Complex numbers
Olympiad
Olympiad
Ex.1568An ellipse via a modulus equation
#ellipse #locus #modulus
Complex numbers
Olympiad
Olympiad
Ex.1569Equilateral triangle condition
#equilateral triangle #complex #roots of unity
Complex numbers
Olympiad
Olympiad
Ex.1570A locus involving an angle
#locus #angle #complex
Complex numbers
Olympiad
Olympiad
Ex.1571A region in the complex plane
#region #inequality #geometric
Complex numbers
Olympiad
Olympiad
Ex.1572The modulus of a sum
#modulus #sum #inequality
Complex numbers
Olympiad
Olympiad
Ex.1573Product formula for cosines
#product formula #cosines #trigonometric
Complex numbers
Olympiad
Olympiad
Ex.1574Sum of a trigonometric series
#trigonometric series #complex #geometric
Complex numbers
Olympiad
Olympiad
Ex.1575Square roots of complex numbers
#square roots #complex #system
Complex numbers
L1
L1
Ex.1576Sum of cosines
#trigonometric sum #cosines #complex
Complex numbers
Olympiad
Olympiad
Ex.1577Trigonometric identities via complex numbers
#De Moivre #trigonometric identities #complex
Complex numbers
Olympiad
Olympiad
Ex.1932Binomial coefficients in steps of three
#roots of unity filter #binomial coefficients #complex numbers
Complex numbers
Olympiad
Olympiad
Ex.1937The product of sin(kπ/n)
#roots of unity #trigonometric product #cyclotomic
Complex numbers
Olympiad
Olympiad
Ex.2103Solving a trigonometric equation via cubics
#trigonometric equation #cubic #cos
Complex numbers
Olympiad
Olympiad
Ex.2104The Julia set of $z\mapsto z^2$
#Julia set #iteration #complex dynamics
Complex numbers
Olympiad
Olympiad
Ex.2105The Möbius transformation
#Möbius #complex #transformation
Complex numbers
M1
M1
Ex.2106A product formula for sines
#product formula #sine #roots of unity
Complex numbers
Olympiad
Olympiad
Ex.2107Integrating over the unit circle
#unit circle #parametrization #integration
Complex numbers
Olympiad
Olympiad