Question

2 cos square theta +cos theta - 1 =0. Find the value of theta.

Answer 1

Answer:

2 cos square theta + cos theta -1 =0

or, 2 cos square theta +(2-1) cos theta -1 =0

or, 2 cos square theta + 2 cos theta - cos theta -1 =0

or, 2 cos theta ( cos theta + 1 ) -1 ( cos theta + 1 ) =0

or, ( 2 cos theta -1) (cos theta +1) =0

either,                                                        or,

cos theta = 1/2                                          cos theta = -1

theta = 60 degree ,                                   theta =180 degree

thus, the value of theta : 60 , 180 degree

Step-by-step explanation:

Answer 2

Answer:

Step-by-step explanation:

2cos^2 theta+ cos theta -1=0  [let cos theta be x]

now we can re write this expression as,

2x^2 +x-1=0

2x^2+2x-x-1=0

2x(x+1)-1(x+1)=0

(x+1) (2x-1)=0

x=1/2 or x=-1

so if cos theta=1/2 theta must be 60 degree

and id cos theta =-1 theta must be 180 degree

hope this helps