Trigonometry?

it says: knowing that tg(-x)-1/2.....=sqrt2/2 and x E ]-3pi/2...[, determine the exact value of 5sen.....(3pi-x) it would be easier to solve others if i knew how to solve this. thank you.
Answers

Captain Matticus, LandPiratesInc

cos(-pi/2 - x) => cos(-(pi/2 + x)) => cos(pi/2 + x) => cos(pi/2)cos(x) - sin(pi/2)sin(x) => -sin(x) sin(pi + x) => sin(pi)cos(x) + sin(x)cos(pi) => -sin(x) tan(-x) - (1/2) * cos(-pi/2 - x) + (1/2) * sin(pi + x) = (sqrt(2)/2) * e -tan(x) - (1/2) * (-sin(x)) + (1/2) * (-sin(x)) = (sqrt(2)/2) * e -tan(x) + (1/2) * sin(x) - (1/2) * sin(x) = (sqrt(2)/2) * e -tan(x) = (sqrt(2)/2) * e 5 * sin(x - pi/2) - 2 * cos(-pi - x) + sin(3pi - x) => 5 * (sin(x)cos(pi/2) - sin(pi/2)cos(x)) - 2 * cos(pi + x) + sin(3pi)cos(x) - sin(x)cos(3pi) => 5 * (-cos(x)) - 2 * (cos(pi)cos(x) - sin(pi)sin(x)) - (-sin(x)) => -5 * cos(x) - 2 * (-cos(x)) + sin(x) => -5 * cos(x) + 2 * cos(x) + sin(x) => sin(x) - 3 * cos(x) => cos(x) * (sin(x)/cos(x) - 3) => 1/(1/cos(x)) * (tan(x) - 3) => (1/sec(x)) * (tan(x) - 3) => (tan(x) - 3) / sqrt(1 + tan(x)^2) => ((sqrt(2)/2) * e - 3) / sqrt(1 + (1/2) * e^2) => (1/2) * (sqrt(2) * e - 6) / sqrt((1/2) * (2 + e^2)) => (1/2) * (sqrt(2) * e - 6) / (sqrt(1/2) * sqrt(2 + e^2)) => (sqrt(2)/2) * (sqrt(2) * e - 6) / sqrt(2 + e^2) => (2e - 6 * sqrt(2)) / (2 * sqrt(2 + e^2)) => (e - 3 * sqrt(2)) / sqrt(2 + e^2)