Added Trig Functions

Adds cot, sec, csc, and their inverse functions.

README.md

@@ -41,7 +41,7 @@ calc supports all the standard stuff, and I'm definitely adding more later (also
 `+`, `-`, `*`, `/`, `^`, `%`
 
 ##### Functions
-`sin`, `cos`, `tan`, `asin`, `acos`, `atan`, `sqrt`, `log`, `lg`, `ln`, `abs`
+`sin`, `cos`, `tan`, `cot`, `sec`, `csc`, `asin`, `acos`, `atan`, `acot`, `asec`, `acsc`, `sqrt`, `log`, `lg`, `ln`, `abs`
 
 ##### Constants
 `e`, `pi`, `π`

operators/functions/trig.go

@@ -36,6 +36,33 @@ var (
 			return math.Tan(args[0])
 		},
 	}
+	cot = &operators.Operator{
+		Name:          "cot",
+		Precedence:    0,
+		Associativity: operators.L,
+		Args:          1,
+		Operation: func(args []float64) float64 {
+			return 1 / math.Tan(args[0])
+		},
+	}
+	sec = &operators.Operator{
+		Name:          "sec",
+		Precedence:    0,
+		Associativity: operators.L,
+		Args:          1,
+		Operation: func(args []float64) float64 {
+			return 1 / math.Cos(args[0])
+		},
+	}
+	csc = &operators.Operator{
+		Name:          "csc",
+		Precedence:    0,
+		Associativity: operators.L,
+		Args:          1,
+		Operation: func(args []float64) float64 {
+			return 1 / math.Sin(args[0])
+		},
+	}
 	asin = &operators.Operator{
 		Name:          "asin",
 		Precedence:    0,
@@ -63,13 +90,46 @@ var (
 			return math.Atan(args[0])
 		},
 	}
+	acot = &operators.Operator{
+		Name:          "acot",
+		Precedence:    0,
+		Associativity: operators.L,
+		Args:          1,
+		Operation: func(args []float64) float64 {
+			return (-90 * ((math.Pi * math.Atan(args[0]) / 90) - math.Pi)) / math.Pi
+		},
+	}
+	asec = &operators.Operator{
+		Name:          "asec",
+		Precedence:    0,
+		Associativity: operators.L,
+		Args:          1,
+		Operation: func(args []float64) float64 {
+			return math.Acos(1 / args[0])
+		},
+	}
+	acsc = &operators.Operator{
+		Name:          "acsc",
+		Precedence:    0,
+		Associativity: operators.L,
+		Args:          1,
+		Operation: func(args []float64) float64 {
+			return math.Asin(1 / args[0])
+		},
+	}
 )
 
 func init() {
 	Register(sin)
 	Register(cos)
 	Register(tan)
+	Register(cot)
+	Register(sec)
+	Register(csc)
 	Register(asin)
 	Register(acos)
 	Register(atan)
+	Register(acot)
+	Register(asec)
+	Register(acsc)
 }