# complex numbers - product of polar forms

• April 10th 2011, 01:04 PM
kassums17
complex numbers - product of polar forms
perform the operation and leave in trigonometric form:

(cos 5°+i sin 5°)(cos 20°+i sin 20°)
• April 10th 2011, 01:06 PM
Plato
Quote:

Originally Posted by kassums17
perform the operation and leave in trigonometric form:
(cos 5°+i sin 5°)(cos 20°+i sin 20°)

• April 10th 2011, 01:08 PM
kassums17
how do you find the cos of 5 degrees and the cos of 20 degrees?
• April 10th 2011, 01:13 PM
Plato
Quote:

Originally Posted by kassums17
how do you find the cos of 5 degrees and the cos of 20 degrees?

There is no need to bother with that.
What does $\left[ {r(\cos (\phi ) + i\sin (\phi ))} \right]\left[ {s(\cos (\theta ) + i\sin (\theta ))} \right] = ~?$