OpenStudy (anonymous):

Trig help? Fan & medal :))

4 years ago
OpenStudy (anonymous):

Solve the following equation for 0</= x </= π : 4cos^2x - 3cosx = 0 . Select all that apply 0 π/6 π/2 5π/6

4 years ago
OpenStudy (anonymous):

Please help me understand as well

4 years ago
OpenStudy (anonymous):

so first step would be to pull out the common factor of cosx (4cosx-3)(cosx)=0 then solve for the roots. cosx=0 when x=pi/2,3pi/2,5pi/2..... in this case only pi/2 matters then the trickier bit is solving for 4cosx-3=0 so 4cosx=3 then cosx=3/4 x=cos^-1(3/4). unfortunately, this doesnt come out as a nice value but x=0.722734248 rad which isn't an answer choice..

4 years ago
OpenStudy (anonymous):

hmmm a little confused lol

4 years ago
OpenStudy (anonymous):

it'd supposed to be in radians not decimals

4 years ago
OpenStudy (anonymous):

the answer

4 years ago
OpenStudy (anonymous):

so the function has multiple roots. one at pi/2 radians and one at about .722 radians. 3/4 is not at a nice angle when you are looking at a unit circle so it doesn't have a nice fractional answer. .722, while a decimal, is still a value in radians

4 years ago