what is 7-2i in trig form?

Question

and
if u=3j and v=7i+j
what is the dot product of u times v
don't get this one because there are no i terms for u

thanks

Answer 1

I am not sure what you mean by the "trig form" of a complex number. The magnitude is sqrt(7^2 + 2^2) = sqrt53
The complex unit vector is e^(i*theta)
where theta = arcsin(-2/7) - -16.6 degrees or -0.29 radians

Thus 7 -2i = sqrt53*e^-0.29i

In the second questiuon, you seem to be talking about two-dimensional vectors, not complex numbers

The dot product is
u*v = 7*0 + 3*1 = 3

Answer 2

Here is a nice webpage that shows how to do the first one, just follow their example #1 with your number.
For some strange reason, they use j instead of i to represent the complex component of the number.

As for your second question , how about
u = 0i + 3j, now you have an i-term.

Answer 3

silly me, forgot to include the link

http://www.intmath.com/complex-numbers/4-polar-form.php