Question

The solution of the equation \(\cos ^2 \theta +\sin \theta +1=0\), lies in the interval

a)(-\(\pi\)/4, \(\pi\)/4)
b)(\(\pi\)/4, 3\(\pi\)/4)
c)(3\(\pi\)/4, 5\(\pi\)/4)
d)(5\(\pi\)/4, 7\(\pi\)/4)

Answer 1

cos^2 + sin^2 = 1

Answer 2

oh, I wrote the question wrong!

Answer 3

I have corrected it now!

Answer 4

@estudier

Answer 5

Use cos^2 + sin^2 = 1 to rewrite, solve quadratic..

Answer 6

change the \(\large cos^2\theta \rightarrow 1-sin^2\theta \).
now you have a trignometric equation in quadratic form..
solve the quadratic.

Answer 7

I am being unable to solve the quadratic equation..

Answer 8

You cannot solve x^2-x-2 where x= sin theta?

Answer 9

yeah, i can.. I was making a silly mistake...

Answer 10

Happens to us all.....