(1) 4 cos x - cos x = 2

3 cos x = 2

cos x = 2/3

basic angle x = 48.19

Note that cos x is positive , thus it can be either in the first quadrant or the fourth quadrant .

therefore , x = 48

or

x = 360 - 48.19

=311.81

= 311

(2) 2 cos^2 x - cos x -1 = 0

( 2 cos x + 1 ) ( cos x - 1 ) = 0

cos x = - 1/2 or cos = 1

use the same method to solve .