Answer:
C) 
Step-by-step explanation:
The formula for area is
A=pi * radius ^2
If the diameter is 40, the radius is 20
Therefore

Answer:


Step-by-step explanation:
First we define two generic vectors in our
space:


By definition we know that Euclidean norm on an 2-dimensional Euclidean space
is:

Also we know that the inner product in
space is defined as:

So as first condition we have that both two vectors have Euclidian Norm 1, that is:

and

As second condition we have that:


Which is the same:

Replacing the second condition on the first condition we have:

Since
we have two posible solutions,
or
. If we choose
, we can choose next the other solution for
.
Remembering,

The two vectors we are looking for are:

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