Hello Shawn, Is the equation as follows?: (Pi - a + 0.5 * Sin(2a) )^1/2 Vo = ---------------------------------------- Pi If so then this is how I would approach the problem: First re-write the numerator in the form: (Pi - a + 0.5 * Sin(2a) )^1/2 = ( Pi^2 - a^2 + 0.25 * Sin^2(2a) ) Then recall that: Sin(2a) = Sin(a) * Cos(a) + Cos(a) * Sin(a) = 2 * Sin(a) * Cos (a) and also that: Sin^2(a) + Cos^2(a) = 1 and hence: Sin^2(a) = 1 - Cos^2(a) The rest is just simple algebraic manipulation and substitution of the above trigonometric expressions. I hope that this helps you. Lee Hewitt (Manchester ENGLAND) =================================================== Lee Hewitt Manchester ENGLAND Home E-Mail: LHewitt104@aol.com University E-Mail: L.Hewitt@eee.salford.ac.uk =================================================== ------------------------------------------------------------------------------ ------ I was wondering if there is anyone out there who can help me solve the equasion below for 'a'. I have tried, and I must admit that my math skills are very lacking. I don't know how to work my way around the sine of 'a', and solve for 'a'. Any suggestions or comments would be helpful. BTW, this equasion will be used to derive conduction angle from RMS and intensity. a = conduction angle Vo = RMS Volts I = Relative Intensity Vs = RMS Supply Voltage Pi = Pie (3.14) ( PI - a + .5 sin 2a )^1/2 Vo = Vs ( ------------------ ) ( PI ) ------------------------------------------------------------------------------ --------------------------------