Posted by Crystal on Monday, February 23, 2009 at 7:58pm.
how do you solve for x?
2cos^24x1=0

math (trig)  myschic, Monday, February 23, 2009 at 8:20pm
First find the cos of 24
multiply this by 2
add 1 to the other side
Finally, divide that answer with 1
and... u have the answer!!! whatever that is...

math (trig)  Reiny, Monday, February 23, 2009 at 8:31pm
I am reading your question as
2cos^2 (4x)  1 = 0
so cos^2 (4x) = 1/2
cos 4x = ±1/√2
so 4x must be an angle in each of the 4 quadrants.
but I know cos 45º = 1/√2
so 4x = 45 or 4x = 135 or 4x = 225 or 4x = 315
then
x = 11.25 or x = 33.75 or x=56.25 or x=78.75
the period of cos 4x = 90º
so by adding/subtracting multiples of 90 to any of the above answers will produce other answers
e.g. 33.75 + 90 = 123.75 would be another possible answer
proof:
LS
= 2 cos^2 (4*123.75)  1
= 2cos^2 (495)  1
= 2(1/2)  1
= 0 = RS

math (trig)  mysterychicken, Monday, February 23, 2009 at 8:35pm
just follow my way, its much simpler

math (trig)  Reiny, Monday, February 23, 2009 at 8:53pm
MC, except you don't get the right answer, lol

math (trig)  mysterychicken, Tuesday, February 24, 2009 at 6:35pm
prove it Reiny
:)
my way always works
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