Answer:
cos 4u = co^s2 2u - sin^2 2u
Step-by-step explanation:
cos 4u = co^s2 2u - sin^2 2u
Let 4u = 2x
cos 2x = cos^2 x - sin^ 2 x
cos (x+x) = cos^2 x - sin^ 2 x
Using cos(x+y) = cos(x)cos(y) -sin(x)sin(y)
cos(x) cos(x)- sin(x) sin (x)= cos^2 x - sin^ 2 x
cos^2 (x) -sin^2 (x) =cos^2 x - sin^ 2 x
Since this is true
cos 2x = cos^2 x - sin^ 2 x
This is true
Substituting 4u back for 2x
cos 4u = co^s2 2u - sin^2 2u
This is true
Um Plan B would be two dollars cheaper than plan A ..
I set the equations up like this :
5+2.50x=
24+1.50x=
Only because thats how many movies she plans on watching.
5+2.50(21)=57.50
24+1.50(21)=55.50
There are 
ways of picking 2 of the 10 available positions for a 0. 8 positions remain.
There are 
ways of picking 3 of the 8 available positions for a 1. 5 positions remain, but we're filling all of them with 2s, and there's 
way of doing that.
So we have
The last expression has a more compact form in terms of the so-called multinomial coefficient,
