Roots of Complex Numbers Sec. 6.6c HW: p odd
From last class: The complex number is a third root of –8 The complex number is an eighth root of 1
Definition A complex number v = a + bi is an nth root of z if v = z n If z = 1, then v is an nth root of unity.
Finding nth Roots of a Complex Number If, then the n distinct complex numbers where k = 0, 1, 2,…, n – 1, are the nth roots of the complex number z.
Let’s now do an example… Find the fourth roots of Use the new formula, with r = 5, n = 4, k = 0 – 3, k = 0:
fourth root continued… Find the fourth roots of Use the new formula, with r = 5, n = 4, k = 0 – 3, k = 1:
fourth root continued… Find the fourth roots of Use the new formula, with r = 5, n = 4, k = 0 – 3, k = 2:
fourth root done! Find the fourth roots of Use the new formula, with r = 5, n = 4, k = 0 – 3, k = 3: How would we verify these algebraically???
A new example… Find the cube roots of –1 and plot them. First, rewrite the complex number in trig. form: Use the new formula, with r = 1, n = 3, k = 0 – 2,
third root continued… Find the cube roots of –1 and plot them. First, rewrite the complex number in trig. form: Use the new formula, with r = 1, n = 3, k = 0 – 2,
third root continued… Find the cube roots of –1 and plot them. First, rewrite the complex number in trig. form: Use the new formula, with r = 1, n = 3, k = 0 – 2,
third root done! Find the cube roots of –1 and plot them. Now, how do we sketch the graph??? First, rewrite the complex number in trig. form: Use the new formula, with r = 1, n = 3, k = 0 – 2, The cube roots of –1