add small note for computation

apache · Jul 11, 2019 · 4c45f2f · 4c45f2f
1 parent df3551b
commit 4c45f2f
Showing 1 changed file with 1 addition and 0 deletions.
diff --git a/src/operator/tensor/elemwise_unary_op_trig.cc b/src/operator/tensor/elemwise_unary_op_trig.cc
@@ -217,6 +217,7 @@ MXNET_OPERATOR_REGISTER_BINARY_WITH_SPARSE_CPU_DR(_backward_arccos,
       // f(x) = arccos(x)
       // n: f'(x) = -1/(1-x^2)^1/2
       // f''(x) = f'(x) * x/(1-x^2)
+      // Note: x/(1-x^2) = x * f'(x)^2
       auto dydx = n->inputs[0];
       auto x = n->inputs[1];
       auto dydx_mul_grad_x = nnvm::NodeEntry{n};