True
<span>Cos(A+B)=CosACosB-SinASinB
therefore Cos(A+A)= CosACosA - SinASinA
= Cos^2A - Sin^2A</span>
Let A = {1, 2, 8} and B = {2, 7}.
P ( A ∪ B ) = {1, 2, 7, 8}
= 4/10
= 0.4
Answer: 0.4
Phone card = $20
You need to minus 17.92 from 20 = $2.08
$2.08 / 0.13 = how many minutes
= 16