diff --git a/index.json b/index.json
index 80ff476..c9ce96e 100644
--- a/index.json
+++ b/index.json
@@ -49,6 +49,8 @@
   },
   "bencode": {
   },
+  "cmath": {
+  },
   "colorize": {
   },
   "configs": {
diff --git a/rbi/annotations/cmath.rbi b/rbi/annotations/cmath.rbi
new file mode 100644
index 0000000..41b06ef
--- /dev/null
+++ b/rbi/annotations/cmath.rbi
@@ -0,0 +1,62 @@
+# typed: true
+
+module CMath
+  include ::Math
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.acos(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.acosh(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.asin(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.asinh(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.atan(z); end
+
+  sig { params(y: Numeric, x: Numeric).returns(Float) }
+  def self.atan2(y, x); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.atanh(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.cbrt(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.cos(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.cosh(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.exp(z); end
+
+  sig { params(z: Numeric, b: Numeric).returns(Float) }
+  def self.log(z, b = ::Math::E); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.log10(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.log2(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.sin(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.sinh(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.sqrt(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.tan(z); end
+
+  sig { params(z: Numeric).returns(Float) }
+  def self.tanh(z); end
+end