Updated: 2026-03-11

Complex Number Calculator: Convert to a+bi Form

Overview: This article explains the conversion of complex numbers from polar to rectangular (a+bi) form. It details the two key representations and provides the mathematical formulas for the conversion process, which is automated by online calculators.

Welcome to our guide on complex number conversion. This resource explains the essential mathematical representations and demonstrates the process to transform numbers from polar to rectangular (a+bi) form.

Understanding the a+bi Form of a Complex Number

Complex numbers are expressed in two primary formats: rectangular form and polar form.

The rectangular form, written as a + bi, identifies a point (a, b) on the complex plane. Here, 'a' is the real component and 'b' is the imaginary component.

The polar form describes the number using magnitude and angle: r × exp(φi). Here, 'r' is the modulus (distance from origin) and 'φ' is the argument (angle with the positive real axis).

A Simple Guide: Converting from Polar to Rectangular Form

To convert a polar form complex number, z = r × exp(iφ), into rectangular a+bi form, apply these formulas derived from trigonometric relationships on the complex plane.

a = r × cos(φ)
b = r × sin(φ)

Calculate the real part 'a' using a = r × cos(φ), and the imaginary part 'b' with b = r × sin(φ).

How to Use a Complex Number Calculator

Using an online a+bi form calculator is efficient. Input the polar coordinates: the magnitude (r) and the phase angle (φ). You can typically choose the angle unit (radians or degrees). The calculator then instantly processes the data and displays the resulting real part 'a' and imaginary part 'b' in the final a + bi format.

Frequently Asked Questions (FAQs)

How do I manually convert a complex number to a+bi form?

Follow a three-step process:

  1. Compute cos(φ) and sin(φ) of the argument φ.
  2. Multiply both results by the magnitude r.
  3. Combine them: a = r × cos(φ) gives the real part, and b = r × sin(φ) gives the imaginary part. The result is a + bi.

What is the rectangular form of exp(iπ/4)?

The rectangular form is √2/2 + (√2/2)i. With a modulus r = 1, and since cos(π/4) = sin(π/4) = √2/2, we get a = 1 × √2/2 and b = 1 × √2/2.

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