For a variable firing angle, sinusoidal supply voltage and load (resistance) the current(RMS), voltage (RMS), the apparent power (Va), power (W), reactive power (Var) and power factor Pf are calculated with this Ti84 Basic program.  

Full wave form and half-wave form modes are available. The triac is assumed to be an ideal switch with no voltage drop and power loss in the triac taken into account. The figure shows the voltage across a load (resistor) at  firing angles of 90 and 270 degrees. For these firing angles, the calculated results for a full wave triac control are shown. Vrms=230 V and R=529 Ω.