It's from the formula we obtained for tan(alpha + beta \2). You just plug in the values of alpha and beta into the sin and cos equation.May i ask how you got this? I got as far as to understanding that 3pi/12 and 2pi/12 are used because we know their values using pythagoras triangles
Sorry DrDusk but I think I will have to go with this one. Stupid_girl's got a point.I guess the question is not expecting you to apply trigonometric identities for product to sum or sum to product. Otherwise, there's no point to bring complex number into the question. Having said that, I think a trigonometric approach is more elegant, especially for the second part of the question.