diff --git a/graph_framework/arithmetic.hpp b/graph_framework/arithmetic.hpp
index 01d2ab34d72a5aa3f278dffbe50fd09f8fc2aabf..429d37d361d8010899d6b6c048576834246736ce 100644
--- a/graph_framework/arithmetic.hpp
+++ b/graph_framework/arithmetic.hpp
@@ -520,6 +520,20 @@ namespace graph {
                                 pow(prm->get_left(), pl->get_right()));
                     }
                 }
+
+//  cos(x)^2 + sin(x)^2 -> 1
+//  sin(x)^2 + cos(x)^2 -> 1
+                auto plrc = constant_cast(pl->get_right());
+                if (plrc.get() && plrc->is(static_cast<T> (2.0))) {
+                    auto pls = sin_cast(pl->get_left());
+                    auto prc = cos_cast(pr->get_left());
+                    auto plc = cos_cast(pl->get_left());
+                    auto prs = sin_cast(pr->get_left());
+                    if ((pls.get() && prc.get() && pls->get_arg()->is_match(prc->get_arg())) ||
+                        (plc.get() && prs.get() && plc->get_arg()->is_match(prs->get_arg()))) {
+                        return one<T, SAFE_MATH> ();
+                    }
+                }
             }
 
 //  (a/y)^e + b/y^e -> (a^2 + b)/(y^e)
diff --git a/graph_tests/arithmetic_test.cpp b/graph_tests/arithmetic_test.cpp
index 3417578940e052bffb84e17b3b0a4ab5f1941a5c..1d25ed429f53c319939edacdfe9349155e39250b 100644
--- a/graph_tests/arithmetic_test.cpp
+++ b/graph_tests/arithmetic_test.cpp
@@ -433,6 +433,19 @@ template<jit::float_scalar T> void test_add() {
     assert(common_power_factor4_cast->get_left()->is_match(var_b*var_b +
                                                            var_c*var_c) &&
            "Expected b^2 + c^2 on the left.");
+
+//  cos(x)^2 + sin(x)^2 -> 1
+    auto trig = graph::cos(var_a)*graph::cos(var_a)
+              + graph::sin(var_a)*graph::sin(var_a);
+    auto trig_cast = graph::constant_cast(trig);
+    assert(trig_cast.get() && "Expected a constant node.");
+    assert(trig_cast->is(static_cast<T> (1.0)) && "Expected 1.");
+//  sin(x)^2 + cos(x)^2 -> 1
+    auto trig2 = graph::sin(var_a)*graph::sin(var_a)
+               + graph::cos(var_a)*graph::cos(var_a);
+    auto trig2_cast = graph::constant_cast(trig2);
+    assert(trig2_cast.get() && "Expected a constant node.");
+    assert(trig2_cast->is(static_cast<T> (1.0)) && "Expected 1.");
 }
 
 //------------------------------------------------------------------------------