diff --git a/src/cgmath/angle.rs b/src/cgmath/angle.rs
index c7a64d2..ad71f15 100644
--- a/src/cgmath/angle.rs
+++ b/src/cgmath/angle.rs
@@ -63,7 +63,7 @@ pub trait Angle
     S: Float
 >
 :   Clone + Zero
-+   Eq + Ord
++   Eq + Equiv<Self> + Ord
 +   ApproxEq<S>
 +   Neg<Self>
 +   ToRad<S>
@@ -144,6 +144,18 @@ impl<S: Float> Deg<S> {
     #[inline] pub fn turn_div_6() -> Deg<S> { Angle::turn_div_6() }
 }
 
+impl<S: Float> Equiv<Rad<S>> for Rad<S> {
+    fn equiv(&self, other: &Rad<S>) -> bool {
+        self.normalize() == other.normalize()
+    }
+}
+
+impl<S: Float> Equiv<Deg<S>> for Deg<S> {
+    fn equiv(&self, other: &Deg<S>) -> bool {
+        self.normalize() == other.normalize()
+    }
+}
+
 impl<S: Float> Angle<S> for Rad<S> {
     #[inline] fn from<A: Angle<S>>(theta: A) -> Rad<S> { theta.to_rad() }
     #[inline] fn full_turn() -> Rad<S> { rad(Real::two_pi()) }
diff --git a/src/tests/angle.rs b/src/tests/angle.rs
index 0b34dc3..19f7f60 100644
--- a/src/tests/angle.rs
+++ b/src/tests/angle.rs
@@ -16,10 +16,21 @@
 use cgmath::angle::*;
 
 #[test]
-fn angle_conv() {
+fn conv() {
     assert_approx_eq!(deg(-5.0).to_rad().to_deg(), deg(-5.0));
     assert_approx_eq!(deg(30.0).to_rad().to_deg(), deg(30.0));
 
     assert_approx_eq!(rad(-5.0).to_deg().to_rad(), rad(-5.0));
     assert_approx_eq!(rad(30.0).to_deg().to_rad(), rad(30.0));
 }
+
+#[test]
+fn equiv() {
+    assert!(Deg::<f32>::full_turn().equiv(&-Deg::<f32>::full_turn()))
+    assert!(Deg::<f32>::turn_div_2().equiv(&-Deg::<f32>::turn_div_2()))
+    assert!(Deg::<f32>::turn_div_3().sub_a(Deg::<f32>::full_turn()).equiv(&Deg::<f32>::turn_div_3()))
+
+    assert!(Rad::<f32>::full_turn().equiv(&-Rad::<f32>::full_turn()))
+    assert!(Rad::<f32>::turn_div_2().equiv(&-Rad::<f32>::turn_div_2()))
+    assert!(Rad::<f32>::turn_div_3().sub_a(Rad::<f32>::full_turn()).equiv(&Rad::<f32>::turn_div_3()))
+}