Question

How do I solve 20cos squared x+cos x-1=0 [0,pi]

Answer 1

can you solve quadratics ?
this is quadratic in cos x ....

Answer 2

really?

Answer 3

a=20,b=1,c=-1?

Answer 4

yes!
cos x = -b+//sqrt b^2-4ac /2a....
i think you know the formula...

Answer 5

I got -1/4 and 1/5(is that the end of the problem)?

Answer 6

correct!
so,
x = cos inverse of -1/4
x=cos inverse of 1/5

Answer 7

do you have choices/options?

Answer 8

nope

Answer 9

it is open-ended

Answer 10

so would the answers be cos inverse=-1/4,1/5?

Answer 11

yeah

Answer 12

that's it?

Answer 13

like this:
x = cos inverse of -1/4
x=cos inverse of 1/5

Answer 14

ty so much

Answer 15

welcome :)