I can solve trig. equations algebraically and , in theory, I know how to solve them graphically, but thanks to difficulty in choosing a suitable vertical/horizontal scale and/or a shaky hand when drawing the curves I cannot read off the intersection of the graphs with sufficient accuracy. Problem example: 3cos2x=0.65 ( x is greater than or equal to -pi and x is less than or equal to pi). Answer given in textbook as -2.47,-0.68,0.68,2.47. How accurate do you have to be if not using a calculator?? Help would really be appreciated