Question 769869
Solve 10cosx^2-12cosx-7=0. Use degrees and round your answer to the nearest hundredth.
10cos^2x-12cosx-7=0
use quadratic formula to solve for cosx
{{{cosx = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
a=10, b=-12, c=-7
Ans:
cosx=1.629 (reject, -1 < cosx < 1)
or
cosx=-0.430