Question #c88fc

1 Answer
Apr 26, 2017

50.1o,154.3o,205.7o,309.0o

Explanation:

Start by completing the square as this expression cannot be factorised.

3cos2x+cosx1=0

cos2x+13cosx13=0

(cosx16)213613=0

(cosx16)2=1336

cosx16=±1336

cosx=16±136

cosx=16(1±13)

Now we look at a graph to see where the solutions will lie.

Geogebra

The graph shows solutions in radians. Solutions in degrees are as follows

50.1o,154.3o,205.7o,309.0o