# How can i solve this equation: 2sen^2(t)-cos(t)-1=0 ?

##### 3 Answers

If you meant

#### Explanation:

After applying the hint you will get

This is

substituting

#### Explanation:

Replace

Solve this quadratic equation for cos t:

Since a - b + c = 0, use shortcut. The 2 real roots are:

a. cos t = -1

Unit circle gives -->

b.

Trig table and unit circle give -->

An odd multiple of

#### Explanation:

using

cos t = -1, 1/2 = cos pi, cos pi/3# and these give

#= an odd multiple of pi, ( 6k +- 1)pi/3.

The list near 0 is

#t = .....- 7/3pi, - 5/3pi,- pi, - pi/3, pi/3, pi, 5/3pi, ...

See graph, for t-intercepts as solutions.

graph{y-2 (sin(x))^2 +cos (x) + 1=0[-10 10 -5 5]}