Question

what is X when 2sin^2(X)+9cos(X)+3=0

Answer 1

have you subbed \(\sin^2 x x = 1-\cos^2 x\) into the eq to simplify it into a quadratic eq?

Answer 2

no i haven't but i'll try it out right now thanks :)

Answer 3

u r welcome. The solution should be trivial after the substitution. :)

Answer 4

I tried it but i still don't get it..

Answer 5

subbing, you should get,
\(2-2\cos^2 x + 9 \cos x +3=0\)
which equals, \(-2\cos^2 x + 9 \cos x +5=0\)
let u = cos x
the equation becomes
\(-2u^2 + 9 u +5=0\)
which is a quadratic equation of u. You can use the general formula to solve for u.

Answer 6

thanks o much.. i really appreciate it

Answer 7

you're welcome :)