Trigonometry Study Guide? Help please?

Question

1.
Write the complex number in polar form. Express the argument in degrees.
-6+8i
A. 10(cos 126.9deg+ isin 126.9deg)
B. 10(cos 53.1deg+isin53.1deg)
C. 10(cos 306.9deg + isin306.9deg)
D. 10(cos 233.1 deg+isin 233.1deg)

2.
Write the complex number in rectangular form
7(cos 120+isin120)

Answer 1

2.
7(cos(120º) + isin(120º))

7(c(90º+30º) + isin(90º+30º))

= 7(-sin30º +icos30º)

= 7(-1/2 + (i√3)/2)

= -7/2(1 + i√3 )

Answer 2

1. -6 + 8i
= 10(-3/5 + 4i/5)
= 10(cos(cos^-1(-3/5)) + i(sin(sin^-1(4/5)).
As cosine is negative and sine is positive, our argument is in the second quadrant.

Option A is the right answer.
 A: 10(cos(126.9º) + isin(126.9º)).

Answer 3

The complex number - 6 + 8i

The polar form of complex number z = a + bi is

a = -6 , b = 8

Since a < 0,Use the formula

Find absolute value of r.

Now find the argument

Polar form of -6 + 8i is

Option A is correct answer.