Answer:
63
Step-by-step explanation:
5 x 13 = 63
is this what you asked for?
Answer:
undefined slope
Step-by-step explanation:
The points contain the same x-value. This means that the line is vertical.
All vertical lines have an undefined slope.
Hope this helps.
Recall the Maclaurin expansion for cos(x), valid for all real x :

Then replacing x with √5 x (I'm assuming you mean √5 times x, and not √(5x)) gives

The first 3 terms of the series are

and the general n-th term is as shown in the series.
In case you did mean cos(√(5x)), we would instead end up with

which amounts to replacing the x with √x in the expansion of cos(√5 x) :
