var pOption = true;

  function calcular_vol_trap() {
	formTrap = document.form_vol_trap;
    if (pOption == true) {
		// calculo a partir das internas
        a_value = parseFloat(formTrap.A.value);		
        b_value = parseFloat(formTrap.B.value);
        c_value = parseFloat(formTrap.C.value);
        d_value = parseFloat(formTrap.D.value);			
        volume = ( (((d_value + c_value)/2) * b_value * a_value) ) / 1000;
        formTrap.VOLUME.value = volume;
        if ( formTrap.ESPESSURA.value != "") {
            espessura = parseFloat(formTrap.ESPESSURA.value/10);

			minibase = espessura * (d_value - c_value)/b_value;
			miniespessura = Math.sqrt(minibase * minibase + espessura * espessura);
            formTrap.H.value = d_value + espessura + minibase + miniespessura;
            formTrap.E.value = b_value + 2*espessura;		
            formTrap.F.value = a_value + 2*espessura;
            formTrap.G.value = c_value + espessura - minibase + miniespessura;	
			
			diferenca = d_value - c_value;
            formTrap.J.value = 2 * miniespessura + Math.sqrt(b_value * b_value + diferenca * diferenca);
			angulo = Math.atan(espessura/minibase)*180/Math.PI;

			formTrap.ANGULO.value = angulo;

        }

    } else {
		// calculo a partir das externas
        f_value = parseFloat(formTrap.F.value);		
        e_value = parseFloat(formTrap.E.value);
        g_value = parseFloat(formTrap.G.value);
        h_value = parseFloat(formTrap.H.value);

        if ( formTrap.ESPESSURA.value != "") {
            espessura = parseFloat(formTrap.ESPESSURA.value/10);
            //** l_value = base do triangulo formado pela tampa traseira
            //** vamos impor que l_value seja metade da espessura
            // *** V = ((D + C)*B/2)*A/1000

            // mostrando valores aproximados nas medidas internas

			minibase = espessura * (h_value - g_value)/e_value;
			miniespessura = Math.sqrt(minibase * minibase + espessura * espessura);

            c_value = g_value - espessura + minibase - miniespessura;
            b_value = e_value - 2*espessura;
            d_value = h_value - espessura - minibase - miniespessura;
            a_value = f_value - 2*espessura;
            formTrap.C.value = c_value;
            formTrap.B.value = b_value;		
            formTrap.D.value = d_value;
            formTrap.A.value = a_value;

			volume = ( (((d_value + c_value)/2) * b_value * a_value) ) / 1000;
            formTrap.VOLUME.value = volume;
			angulo = Math.atan(espessura/minibase)*180/Math.PI;

			formTrap.ANGULO.value = angulo;

        }

    }
  
  }
  
  function checaCampos(ind) {
	  formTrap = document.form_vol_trap;
      formTrap.aPartirDasMedidas.options[ind].selected = true;
      formTrap.VOLUME.value = "";

	  if ( formTrap.aPartirDasMedidas.value == "0" ) {
	  	// 0 indica a partir das medidas internas
	  	// 1 indica a partir das medidas externas
		  pOption = true;
      	  formTrap.A.disabled = false;
          formTrap.A.style.backgroundColor = "#FFFFFF";
          formTrap.B.disabled = false;
          formTrap.B.style.backgroundColor = "#FFFFFF";
          formTrap.C.disabled = false;
          formTrap.C.style.backgroundColor = "#FFFFFF";
          formTrap.D.disabled = false;
          formTrap.D.style.backgroundColor = "#FFFFFF";
          with (formTrap.E) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formTrap.F) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formTrap.G) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formTrap.H) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          formTrap.J.value = "";
	  }	 else {
	      pOption = false;
          with (formTrap.A) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formTrap.B) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formTrap.C) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formTrap.D) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          formTrap.E.disabled = false;
          formTrap.E.style.backgroundColor = "#FFFFFF";
          formTrap.F.disabled = false;
          formTrap.F.style.backgroundColor = "#FFFFFF";
          formTrap.G.disabled = false;
          formTrap.G.style.backgroundColor = "#FFFFFF";
          formTrap.H.disabled = false;
          formTrap.H.style.backgroundColor = "#FFFFFF";
          formTrap.J.value = "";
	  
	  }
      
  }

  function trocaClass(bool) {
      if (bool == true) {
        return "inputboxDisabled";
      } else {
       return "inputbox";
      }
  }




  function calcular_vol_cubo() {
	formCubo = document.form_vol_cubo;
    if (pOption == true) {
		// calculo a partir das internas
		volume = (parseFloat(formCubo.A.value) *  parseFloat(formCubo.B.value) *  parseFloat(formCubo.C.value)) / 1000;
		formCubo.VOLUME.value = volume.toFixed(2);
		if ( formCubo.ESPESSURA.value != "") {
			espessura = (formCubo.ESPESSURA.value/10);
			b_value = parseFloat(formCubo.B.value);
			a_value = parseFloat(formCubo.A.value);		
			c_value = parseFloat(formCubo.C.value);					
			formCubo.E.value = b_value + 2*espessura;
			formCubo.F.value = a_value + 2*espessura;
			formCubo.G.value = c_value + 2*espessura;
		}

	} else {
		// calculo a partir das externas
        f_value = parseFloat(formCubo.F.value);		
        e_value = parseFloat(formCubo.E.value);
        g_value = parseFloat(formCubo.G.value);


        if ( formCubo.ESPESSURA.value != "") {
            espessura = parseFloat(formCubo.ESPESSURA.value/10);

            c_value = g_value - 2*espessura;
            b_value = e_value - 2*espessura;
            a_value = f_value - 2*espessura;
            formCubo.C.value = c_value;
            formCubo.B.value = b_value;		
            formCubo.A.value = a_value;

			volume = ( a_value * b_value * c_value)  / 1000;
            formCubo.VOLUME.value = volume.toFixed(2);
        }

	}
  }

  function checaCamposRetangulo(ind) {
	  formCubo = document.form_vol_cubo;
      formCubo.aPartirDasMedidas.options[ind].selected = true;
      formCubo.VOLUME.value = "";
	  if ( formCubo.aPartirDasMedidas.value == "0" ) {
		  pOption = true;
      	  formCubo.A.disabled = false;
          formCubo.A.style.backgroundColor = "#FFFFFF";
          formCubo.B.disabled = false;
          formCubo.B.style.backgroundColor = "#FFFFFF";
          formCubo.C.disabled = false;
          formCubo.C.style.backgroundColor = "#FFFFFF";
          with (formCubo.E) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formCubo.F) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formCubo.G) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }

	  }	 else {
	      pOption = false;
          with (formCubo.A) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formCubo.B) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          with (formCubo.C) {
              disabled = true;
              style.backgroundColor = "#D2D2D2";
              value = "";
          }
          formCubo.E.disabled = false;
          formCubo.E.style.backgroundColor = "#FFFFFF";
          formCubo.F.disabled = false;
          formCubo.F.style.backgroundColor = "#FFFFFF";
          formCubo.G.disabled = false;
          formCubo.G.style.backgroundColor = "#FFFFFF";
	  
	  }
      
  }