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
Step-by-step explanation:
Vina has $4.70 in quarters, dimes and nickels in her purse. She has nine more dimes than quarters and four more nickels than quarters. How many of each coin are in her purse?
nickels
dimes
quarters
Answer:
1st option: 55 + 19.50m = 250
Step-by-step explanation:
Answer:
j-4 is how you show 4 less than a number j
