280*3= 840
3 journals is about 840 grams
Answer:
8.008
8.018
8.088
8.808
8.88
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We are given with the following:
Effective annual interest, i = 0.0425
Future worth, F = $25000
Number of years, n = 18
We use the formula to solve for the present worth of the money:
P = F / (1 + i)^n
P = 25000 / (1 + 0.0425)^18
P = 11818.73
The closest answer is:
<span>b.
$11,820</span>
cos4x = cos2x
We know that:
cos2x = 1-2cos^2 x
==> cos4x = 1-2cos^2 (2x)
Now substitute:
==> 1-2cos^2 (2x) = cos2x
==> 2cos^2 (2x) + cos2x - 1 = 0
Now factor:
==> (2cos2x -1)(cos2x + 1) = 0
==> 2cos2x -1 = 0 ==> cos2x =1/2 ==> 2x= pi/3
==> x1= pi/6 , 7pi/6
==> x1= pi/6 + 2npi
==> x2= 7pi/6 + 2npi
==> cos2x = -1 ==> 2x= pi ==> x3 = pi/2 + 2npi.
<span>==> x= { pi/6+2npi, 7pi/6+2npi, pi/2+2npi}</span>
