diff --git a/test/unit/sd59x18/math/cos/cos.t.sol b/test/unit/sd59x18/math/cos/cos.t.sol
new file mode 100644
index 0000000..c0afa6f
--- /dev/null
+++ b/test/unit/sd59x18/math/cos/cos.t.sol
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity >=0.8.19 <0.9.0;
+
+import { sd } from "src/sd59x18/Casting.sol";
+import { PI, ZERO, uUNIT } from "src/sd59x18/Constants.sol";
+import { sqrt } from "src/sd59x18/Math.sol";
+import { cos } from "src/sd59x18/Trigonometry.sol";
+import { SD59x18 } from "src/sd59x18/ValueType.sol";
+
+import { SD59x18_Unit_Test } from "../../SD59x18.t.sol";
+
+contract Cos_Unit_Test is SD59x18_Unit_Test {
+    function cos_Sets() internal returns (Set[] memory) {
+        delete sets;
+        SD59x18 SD1 = sd(1 * uUNIT);
+        SD59x18 SD2 = sd(2 * uUNIT);
+        SD59x18 SD3 = sd(3 * uUNIT);
+        SD59x18 SD4 = sd(4 * uUNIT);
+        SD59x18 SD5 = sd(5 * uUNIT);
+        SD59x18 SD6 = sd(6 * uUNIT);
+        sets.push(set({ x: -PI,             expected: -SD1             })); // cos(-pi) = -1
+        sets.push(set({ x: -PI * SD5 / SD6, expected: -sqrt(SD3) / SD2 })); // cos(-5*pi/6) = -sqrt(3)/2
+        sets.push(set({ x: -PI * SD3 / SD4, expected: -sqrt(SD2) / SD2 })); // cos(-3*pi/4) = -sqrt(2)/2
+        sets.push(set({ x: -PI * SD2 / SD3, expected: -SD1 / SD2       })); // cos(-2*pi/3) = -1/2
+        sets.push(set({ x: -PI / SD2,       expected: ZERO             })); // cos(-pi/2) = 0
+        sets.push(set({ x: -PI / SD3,       expected: SD1 / SD2        })); // cos(-pi/3) = 1/2
+        sets.push(set({ x: -PI / SD4,       expected: sqrt(SD2) / SD2  })); // cos(-pi/4) = sqrt(2)/2
+        sets.push(set({ x: -PI / SD6,       expected: sqrt(SD3) / SD2  })); // cos(-pi/6) = sqrt(3)/2
+        sets.push(set({ x: ZERO,            expected: SD1              })); // cos(0) = 1
+        sets.push(set({ x: PI / SD6,        expected: sqrt(SD3) / SD2  })); // cos(pi/6) = sqrt(3)/2
+        sets.push(set({ x: PI / SD4,        expected: sqrt(SD2) / SD2  })); // cos(pi/4) = sqrt(2)/2
+        sets.push(set({ x: PI / SD3,        expected: SD1 / SD2        })); // cos(pi/3) = 1/2
+        sets.push(set({ x: PI / SD2,        expected: ZERO             })); // cos(pi/2) = 0
+        sets.push(set({ x: PI * SD2 / SD3,  expected: -SD1 / SD2       })); // cos(2*pi/3) = -1/2
+        sets.push(set({ x: PI * SD3 / SD4,  expected: -sqrt(SD2) / SD2 })); // cos(3*pi/4) = -sqrt(2)/2
+        sets.push(set({ x: PI * SD5 / SD6,  expected: -sqrt(SD3) / SD2 })); // cos(5*pi/6) = -sqrt(3)/2
+        sets.push(set({ x: PI,              expected: -SD1             })); // cos(pi) = -1
+        return sets;
+    }
+
+    function test_Cos() external parameterizedTest(cos_Sets()) {
+        assertApproxEqAbs(
+            cos(s.x).intoInt256(),
+            s.expected.intoInt256(),
+            0.000_000_001 ether, // 8 correct decimals
+            "SD59x18 cos"
+        );
+    }
+}
diff --git a/test/unit/sd59x18/math/sin/sin.t.sol b/test/unit/sd59x18/math/sin/sin.t.sol
new file mode 100644
index 0000000..9ae5943
--- /dev/null
+++ b/test/unit/sd59x18/math/sin/sin.t.sol
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity >=0.8.19 <0.9.0;
+
+import { sd } from "src/sd59x18/Casting.sol";
+import { PI, ZERO, uUNIT } from "src/sd59x18/Constants.sol";
+import { sqrt } from "src/sd59x18/Math.sol";
+import { sin } from "src/sd59x18/Trigonometry.sol";
+import { SD59x18 } from "src/sd59x18/ValueType.sol";
+
+import { SD59x18_Unit_Test } from "../../SD59x18.t.sol";
+
+contract Sin_Unit_Test is SD59x18_Unit_Test {
+    function sin_Sets() internal returns (Set[] memory) {
+        delete sets;
+        SD59x18 SD1 = sd(1 * uUNIT);
+        SD59x18 SD2 = sd(2 * uUNIT);
+        SD59x18 SD3 = sd(3 * uUNIT);
+        SD59x18 SD4 = sd(4 * uUNIT);
+        SD59x18 SD5 = sd(5 * uUNIT);
+        SD59x18 SD6 = sd(6 * uUNIT);
+        sets.push(set({ x: -PI,             expected: ZERO             })); // sin(-pi) = 0
+        sets.push(set({ x: -PI * SD5 / SD6, expected: -SD1 / SD2       })); // sin(-5*pi/6) = -1/2
+        sets.push(set({ x: -PI * SD3 / SD4, expected: -sqrt(SD2) / SD2 })); // sin(-3*pi/4) = -sqrt(2)/2
+        sets.push(set({ x: -PI * SD2 / SD3, expected: -sqrt(SD3) / SD2 })); // sin(-2*pi/3) = -sqrt(3)/2
+        sets.push(set({ x: -PI / SD2,       expected: -SD1             })); // sin(-pi/2) = -1
+        sets.push(set({ x: -PI / SD3,       expected: -sqrt(SD3) / SD2 })); // sin(-pi/3) = -sqrt(3)/2
+        sets.push(set({ x: -PI / SD4,       expected: -sqrt(SD2) / SD2 })); // sin(-pi/4) = -sqrt(2)/2
+        sets.push(set({ x: -PI / SD6,       expected: -SD1 / SD2       })); // sin(-pi/6) = -1/2
+        sets.push(set({ x: ZERO,            expected: ZERO             })); // sin(0) = 0
+        sets.push(set({ x: PI / SD6,        expected: SD1 / SD2        })); // sin(pi/6) = 1/2
+        sets.push(set({ x: PI / SD4,        expected: sqrt(SD2) / SD2  })); // sin(pi/4) = sqrt(2)/2
+        sets.push(set({ x: PI / SD3,        expected: sqrt(SD3) / SD2  })); // sin(pi/3) = sqrt(3)/2
+        sets.push(set({ x: PI / SD2,        expected: SD1              })); // sin(pi/2) = 1
+        sets.push(set({ x: PI * SD2 / SD3,  expected: sqrt(SD3) / SD2  })); // sin(2*pi/3) = sqrt(3)/2
+        sets.push(set({ x: PI * SD3 / SD4,  expected: sqrt(SD2) / SD2  })); // sin(3*pi/4) = sqrt(2)/2
+        sets.push(set({ x: PI * SD5 / SD6,  expected: SD1 / SD2        })); // sin(5*pi/6) = 1/2
+        sets.push(set({ x: PI,              expected: ZERO             })); // sin(pi) = 0
+        return sets;
+    }
+
+    function test_Sin() external parameterizedTest(sin_Sets()) {
+        assertApproxEqAbs(
+            sin(s.x).intoInt256(),
+            s.expected.intoInt256(),
+            0.000_000_001 ether, // 8 correct decimals
+            "SD59x18 sin"
+        );
+    }
+}