Grad(f)=x1,x2,-x1(-2btSin[s]+2aCos[s]Sin[bs]+tCos[s]Sin[2bs]+2Cos[s]Cos[bs](a+tCos[bs])
′
g
[t]-g[t](2Cos[s]
2
Sin[bs]
+(2bSin[s]+Cos[s]Sin[2bs])
′
g
[t]))+x2(2btCos[s]+2aSin[s]Sin[bs]+tSin[s]Sin[2bs]+2Cos[bs](a+tCos[bs])Sin[s]
′
g
[t]-g[t](2Sin[s]
2
Sin[bs]
+(-2bCos[s]+Sin[s]Sin[2bs])
′
g
[t]))-(-2(2
2
a
+
2
t
+4
2
b
2
t
+4atCos[bs]+
2
t
Cos[2bs])Sin[bs]+
′
g
[t]((-4
2
a
-(3+4
2
b
)
2
t
)Cos[bs]-t(-4a(-1+
2
b
)+4aCos[2bs]+tCos[3bs])-2(a+tCos[bs])
′
g
[t](2(a+tCos[bs])Sin[bs]+(2aCos[bs]+t(1-2
2
b
+Cos[2bs]))
′
g
[t]))-2(a+tCos[bs])(2
2
a
+
2
t
+2
2
b
2
t
+4atCos[bs]+
2
t
Cos[2bs])
′′
g
[t]-2(-1-2
2
b
+Cos[2bs])
3
g[t]
Sin[bs]
′′
g
[t]+2
2
g[t]
((-1+2
2
b
+Cos[2bs])Sin[bs]-Sin[bs]Sin[2bs]
′
g
[t]+(-1-2
2
b
+Cos[2bs])Sin[bs]
2
′
g
[t]
+Cos[bs](-1-4
2
b
+Cos[2bs])
3
′
g
[t]
+(a+tCos[bs])(-3-2
2
b
+3Cos[2bs])
′′
g
[t])+g[t](-4(a+tCos[bs])(-1+
2
b
+Cos[2bs])+4(2aCos[bs]+t(1-5
2
b
+Cos[2bs]))Sin[bs]
′
g
[t]-2(2a(-1+
2
b
+Cos[2bs])+2tCos[bs](-1+5
2
b
+Cos[2bs]))
2
′
g
[t]
+4(2aCos[bs]+t(1-
2
b
+Cos[2bs]))Sin[bs]
3
′
g
[t]
+2(6
2
a
+(3+2
2
b
)
2
t
+3t(4aCos[bs]+tCos[2bs]))Sin[bs]
′′
g
[t]))(2
2
a
+
2
t
+2
2
b
2
t
+4atCos[bs]+
2
t
Cos[2bs]+2g[t]Sin[bs](-2(a+tCos[bs])+g[t]Sin[bs])+4
2
b
tg[t]
′
g
[t]+(2
2
(a+tCos[bs])
+(1+2
2
b
-Cos[2bs])
2
g[t]
-4(a+tCos[bs])g[t]Sin[bs])
2
′
g
[t]
)(2(a+tCos[bs]-g[t]Sin[bs])(-Cos[bs]+Sin[bs]
′
g
[t]))