# Simplifying and giving answers in cartesian form

• Nov 3rd 2013, 04:44 AM
Question101
Simplifying and giving answers in cartesian form
Hi there i have a question to ask

The following must be simplify and must be answered in cartesian form, present your answer on an argand diagram. Im not too sure how to do these could someone explain it please? thank you :)

Question (a)

(4+5j)(4+5j)

Question (b)

(-5-2j)(5+2j)
• Nov 3rd 2013, 05:41 AM
topsquark
Re: Simplifying and giving answers in cartesian form
Quote:

Originally Posted by Question101
Hi there i have a question to ask

The following must be simplify and must be answered in cartesian form, present your answer on an argand diagram. Im not too sure how to do these could someone explain it please? thank you :)

Question (a)

(4+5j)(4+5j)

Question (b)

(-5-2j)(5+2j)

Just FOIL them out. For example, for a) $\displaystyle (4 + 5j)(4 + 5j) = 4 \cdot 4 + 4 \cdot 5j + 5j \cdot 4 + 5j \cdot 5j$

Then use $\displaystyle j^2 = -1$ and collect like terms.

-Dan