Answer:
28/45
Step-by-step explanation:
Dont worry i also don't feel like doing fractions most the time they can get very annoying when you have to work with a lot of them.
cos (2x) = cos x
2 cos^2 x -1 = cos x using the double angle formula
2 cos ^2 x -cos x -1 =0
factor
(2 cos x+1) ( cos x -1) = 0
using the zero product property
2 cos x+1 =0 cos x -1 =0
2 cos x = -1 cos x =1
cos x = -1/2 cos x=1
taking the arccos of each side
arccos cos x = arccos (-1/2) arccos cos x = arccos 1
x = 120 degrees x=-120 degrees x=0
remember you get 2 values ( 2nd and 3rd quadrant)
these are the principal values
now we need to add 360
x = 120+ 360n x=-120+ 360n x = 0 + 360n where n is an integer
I = PRT
P = 8000
T = 4
R = 12%...turn to decimal...0.12
now we sub
I = (8000)(0.12)(4)
I = 3840 <==
The product of 68 and 21 would be 1,428.
