diff --git a/backend/recommondation.go b/backend/recommondation.go
new file mode 100644
index 0000000..f87cb26
--- /dev/null
+++ b/backend/recommondation.go
@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func cosine(x, y []int) float64 {
+	var dotProduct, normX, normY float64
+	for i := 1; i < len(x); i++ {
+		dotProduct += float64(x[i] * y[i])
+		normX += float64(x[i] * x[i])
+		normY += float64(y[i] * y[i])
+	}
+	return dotProduct / (math.Sqrt(normX) * math.Sqrt(normY))
+}
+
+func main() {
+	history := [][]int{
+		{1, 0, 1, 0},
+		{0, 1, 0, 1},
+		{1, 0, 1, 1},
+	}
+
+	productCategory := [][]int{
+		{1, 1, 0, 0},
+		{0, 0, 0, 1},
+		{0, 0, 1, 0},
+		{0, 0, 1, 1},
+		{0, 1, 0, 0},
+
+		{0, 1, 1, 1},
+		{1, 1, 1, 0},
+		{0, 0, 0, 1},
+		{1, 1, 1, 1},
+	}
+
+	// Calculate similarity between first search and each product
+	for i, product := range productCategory {
+		sim := cosine(history[0], product)
+		fmt.Printf("Similarity with product %d: %f\n", i, sim)
+	}
+}
+
+