The problem statement suggests you use a calculator. A graphing calculator can give the answers you seek.
a) The calculator shows 5 solutions:
{5π/23, 5π/17, 25π/23, 25π/17, 45π/23}
These have approximate decimal values of
{0.6830, 0.9240, 3.4148, 4.6200, 6.1466}
b) The calculator shows 2 solutions with approximate decimal values of
{1.2925, 4.4341}
c) The calculator shows 2 solutions with approximate decimal values of
{1.3694, 4.9137}
_____
This (desmos) calculator displays intercepts to 3 decimal places. Since you want 4 decimal places, some additional refinement of the answer was necessary. That was accomplished using Newton's method iteration. The details are not shown. A suitable graphing calculator (for example, a TI-84) will supply the intercept coordinates to full calculator accuracy.
