diff --git a/math/cos.py b/math/cos.py
new file mode 100644
index 00000000..91e38c58
--- /dev/null
+++ b/math/cos.py
@@ -0,0 +1,56 @@
+# Menghitung cosisnus dengan menggunakan deret taylor
+# https://en.wikipedia.org/wiki/Taylor_series#Trigonometric_functions
+import math
+
+
+def factorial(x) -> int:
+    if x < 0:
+        return ValueError("Angkanya harus bilangan real")
+    if x == 0 or x == 1:
+        return 1
+    else:
+        return x * (factorial(x - 1))
+
+
+def cosinus(sudut) -> float:
+    """
+    Cosinus adalah sebuah perbandingan dari sisi samping dan
+    miring segitiga siku-siku.
+
+    >>> cosinus(0)
+    1.0
+    >>> cosinus(30)
+    0.8660254037844386
+    >>> cosinus(45)
+    0.7071067811865475
+    >>> cosinus(60)
+    0.5000000000000001
+    >>> cosinus(90)
+    -3.3769215522516056e-15
+    """
+    result = 0.0
+    interable = 10
+    radian = sudut * math.pi / 180
+    for i in range(interable):
+        numerator = math.pow(radian, 2 * i) * math.pow(-1, i)
+        detector = factorial(2 * i)
+        result = result + (numerator / detector)
+
+    return float(result)
+
+
+def main(args=None):
+    import doctest
+
+    doctest.testmod()
+
+    # base case
+    print(cosinus(0))  # 1.0
+    print(cosinus(30))  # 0.8660254037844386
+    print(cosinus(45))  # 0.7071067811865475
+    print(cosinus(60))  # 0.5000000000000001
+    print(cosinus(90))  # -3.3769215522516056e-15
+
+
+if __name__ == "__main__":
+    main()