How do I solve W=a sin(0.267) / sin cos( 0.267) when a = 1? I must use the equation w = a sin (0.257) / sin cos (+0.267)

Please show step by step.

The full problem is For a perfect parabolic reflector with an aperture of 1 m and rim angle of 30 o (similar but not identical to the one shown in Problem 1): (a) calculate the image width it produces on a flat receiver placed perpendicular to the axis of the parabola; (b) estimate the geometric concentration ratio for this collector, using the image dimension you found (note that in case of parabolic concentrators, geometric concentration ratio may not be adequate to describe the energy flux concentration); (c) estimate what rim angle would give you the highest geometric concentration ratio