Question 963709
Find the solutions of the given equation in the indicated interval. (Give your answers to two decimal places. Enter your answers as a comma-separated list.)
20 (cos(x))^2 + cos(x) − 1 = 0, [0, π]
***
{{{20cos^2(x)+cosx-1=0}}}
solve for cosx by quadratic formula
{{{cosx = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
a=20, b=1, c=-1
ans:
cosx=-0.25
x=1.82 radians
or 
cosx=0.2
x=1.37 radians