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
Subtract it and you will find your answer hope this helps
Answer:
Step-by-step explanation:
the minimum of f is for x = 1 and f(1)=0
f is decreasing for x<=1 and increasing for x>=1
so the domain is 
x>=1 so x is positive and we can take the square root
so 
To find the original amount, you divide the product by the percentage.
112.79 / 0.15 ≈ 751.933 (the 3's repeat infinitely).
To check your answer, multiply 751.933 by 0.15.
751.933 * 0.15 = 112.78995 ≈ 112.79
omi god..... I used http://convert-to.com/202/speed-units.html and got
1.64 maybe if u try it would be different idk
