Hey lauramorrison93.

Since you know the angle, you can calculate the delta by using information about the relative error.

If something is off by 1% at the most then the delta will be 0.01*45*pi/180 (convert to radians) which is 0.007853 which is the value for delta(A) (in radians)

This means we dS/S = 0.01 + 0.01 + 0.007853 = 0.027853 < 0.028 which proves the claim made above.