diff --git a/Makefile b/Makefile
index ae970a6..842fdf1 100644
--- a/Makefile
+++ b/Makefile
@@ -15,3 +15,17 @@ oclint:
 	bazel build --config=oclint //src/...
 	find bazel-bin/src/**/oclint-analysis/** -name 'analyzed*.txt' -exec cat {} +
 	find bazel-bin/src/**/oclint-analysis/** -name 'metadata.json' -exec cat {} +
+
+patched:
+	bazel build //src/apps:math --define=sin=true
+	# calculate sin
+	bazel-bin/src/apps/math 1
+
+	bazel build //src/apps:math
+	# calculate cos
+	bazel-bin/src/apps/math 1
+
+	bazel clean
+	bazel build //src/apps:math --define=sin=true
+	# calculate sin
+	bazel-bin/src/apps/math 1
diff --git a/patches/BUILD.bazel b/patches/BUILD.bazel
new file mode 100644
index 0000000..a3f4ff1
--- /dev/null
+++ b/patches/BUILD.bazel
@@ -0,0 +1 @@
+exports_files(["math.cc.sin.patch"])
diff --git a/patches/math.cc.sin.patch b/patches/math.cc.sin.patch
new file mode 100644
index 0000000..9268b73
--- /dev/null
+++ b/patches/math.cc.sin.patch
@@ -0,0 +1,14 @@
+diff --git a/src/apps/math.cc b/src/apps/math.cc
+index 41283af..f3823ff 100644
+--- a/src/apps/math.cc
++++ b/src/apps/math.cc
+@@ -5,7 +5,7 @@
+ 
+ int main(int argc, char *argv[]) {
+   double value = std::stod(argv[1]);
+-  double result = gcem::cos(value);
+-  std::cout << "The cos of " << value << " is: " << result << std::endl;
++  double result = gcem::sin(value);
++  std::cout << "The sin of " << value << " is: " << result << std::endl;
+   return 0;
+ }
diff --git a/src/apps/BUILD.bazel b/src/apps/BUILD.bazel
index a22f377..829c2b4 100644
--- a/src/apps/BUILD.bazel
+++ b/src/apps/BUILD.bazel
@@ -18,9 +18,28 @@ sh_binary(
     srcs = ["release_metadata.sh"],
 )
 
+config_setting(
+    name = "sin",
+    values = {"define": "sin=true"},
+)
+
+genrule(
+    name = "math_maybe_patched",
+    srcs = [
+        "math.cc",
+        "//patches:math.cc.sin.patch",
+    ],
+    outs = ["math_maybe_patched.cc"],
+    cmd = select({
+        ":sin": "cp $(location math.cc) $@ && patch $@ < $(location //patches:math.cc.sin.patch)",
+        "//conditions:default": "cp $(location math.cc) $@",
+    }),
+    tools = [],
+)
+
 cc_binary(
     name = "math",
-    srcs = ["math.cc"],
+    srcs = [":math_maybe_patched"],
     deps = [
         "@gcem",
     ],