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M.1 U.1 Complex Numbers. What are imaginary numbers?. Viewed the same way negative numbers once were How can you have less than zero? Numbers which square to give negative real numbers.
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What are imaginary numbers? • Viewed the same way negative numbers once were • How can you have less than zero? • Numbers which square to give negative real numbers. • “I dislike the term “imaginary number” — it was considered an insult, a slur, designed to hurt i‘s feelings. The number i is just as normal as other numbers, but the name “imaginary” stuck so we’ll use it.” • Imaginary numbers deal with rotations, complex numbers deal with scaling and rotations simultaneously (we’ll discuss this further later in the week)
Imaginary Numbers • What is the square root of 9? • What is the square root of -9?
Imaginary Numbers • The constant, i, is defined as the square root of negative 1:
Imaginary Numbers • The square root of -9 is an imaginary number...
Imaginary Numbers • Simplify these radicals:
Multiples of i • Consider multiplying two imaginary numbers: • So...
Multiples of i • Powers of i:
i28 i75 i113 i86 i1089 Powers of i - Practice
Solutions Involving i • Solve: • Solve:
Complex Numbers • Have a real and imaginary part . • Write complex numbers as a + bi • Examples: 3 - 7i, -2 + 8i, -4i, 5 + 2i Real = a Imaginary = bi
Add & Subtract • Like Terms • Example: (3 + 4i) + (-5- 2i) = -2 + 2i
Practice Add these Complex Numbers: • (4 + 7i) - (2 - 3i) • (3 - i) + (7i) • (-3 + 2i) - (-3 + i)
Multiplying • FOIL and replace i2 with -1:
Practice Multiply: • 5i(3 - 4i) • (7 - 4i)(7 + 4i)
Division/Standard Form • A complex number is in standard form when there is no i in the denominator. • Rationalize any fraction with i in the denominator. Monomial Denominator: Binomial Denominator:
Rationalizing • Monomial: multiply the top & bottom by i.
Complex #: Rationalize • Binomial: multiply the numerator and denominator by the conjugateof the denominator ... conjugate is formed by negating the imaginary term of a binomial
Practice • Simplify:
Absolute Value of Complex Numbers • Absolute Value is a numbers distance from zero on the coordinate plane. • a = x-axis • b = y axis • Distance from the origin (0,0) = • |z| = √x2+y2 Modulus
Exit Ticket • Simplify (-2+4i) –(3+9i) • Write the following in standard form 8+7i 3+4i • Find the absolute value 4-5i
Homework • Complex Numbers worksheet • For #7, remember the quadratic formula!