True
<span>Cos(A+B)=CosACosB-SinASinB
therefore Cos(A+A)= CosACosA - SinASinA
= Cos^2A - Sin^2A</span>
Answer:
Mean = 30.68
Standard deviation = 6.095
Two standard deviations above the mean = 42.87
Step-by-step explanation:
Given the following data :
21; 21; 22; 23; 24; 24; 25; 25; 28; 29; 29; 31; 32; 33; 33; 34; 35; 36; 36; 36; 36; 38; 38; 38; 40
Mean = Σ(x) / n
n = 25
Σ (X) = 767
Mean (m) = 767 / 25
Mean (m) = 30.68
Standard deviation : sqrt[Σ(x - m) / n]
Using a calculator :
Standard deviation = 6.095 ( 2 decimal places)
2 standard deviations above the mean :
Mean + 2(standard deviation)
Mean + 2(6.095)
30.68 + 12.19
30.68 + 12.19
= 42.87
Answer:
the time Ari spent to walk is
the time Beth spent to walk is
the time Cathy spent to walk is 1h21' = 1.35(h)
so the time Ari spent > Cathy > Beth
=> list: Beth, Cathy, Ari
