diff --git a/src/vector.h b/src/vector.h
index 7dd68dc..8c8b68a 100644
--- a/src/vector.h
+++ b/src/vector.h
@@ -44,6 +44,8 @@ struct vector {
 
 
 bool vector_product(vector *a, vector *b, vector *c);
+bool add_vectors(vector *a, vector *b, vector *c);
+bool sub_vectors(vector *a, vector *b, vector *c);
 bool normalize_vector(vector *a, vector *b);
 bool copy_vector(vector *a, vector *b);