and in the interval [0,2pie)
divide both sides by 12.
cos^2x = 3/12
cos^2x = 1/4
take the square root of both sides.
cosx = 1/2
For what value of x is cos(x) = 1/2? If you know the unit circle, you'll know this is pi/3.
Or in other words...
arccos(1/2) = pi/3.
There is another solution in the fourth quadrant as well, 5pi/3.
12cos^2 x=3
cos^2 x = 3/12 = 1/4
cos x = +/- 1/2
either x = cos^-1 ( 1/2 ) = pi/3 or 5pi/3
or x= cos^-1 ( -1/2) = 2pi/3 or 4pi/3
cos^2x=1/4
cosx=1/2
x=pi/3
x=5pi/3
Comments
divide both sides by 12.
cos^2x = 3/12
cos^2x = 1/4
take the square root of both sides.
cosx = 1/2
For what value of x is cos(x) = 1/2? If you know the unit circle, you'll know this is pi/3.
Or in other words...
arccos(1/2) = pi/3.
There is another solution in the fourth quadrant as well, 5pi/3.
12cos^2 x=3
cos^2 x = 3/12 = 1/4
cos x = +/- 1/2
either x = cos^-1 ( 1/2 ) = pi/3 or 5pi/3
or x= cos^-1 ( -1/2) = 2pi/3 or 4pi/3
cos^2x=1/4
cosx=1/2
x=pi/3
x=5pi/3