From 1b426d79b42b9d2e2a78021400b519a0cb281710 Mon Sep 17 00:00:00 2001
From: Iaroslav <postovalovya@gmail.com>
Date: Sun, 20 Sep 2020 19:31:17 +0700
Subject: [PATCH] Fix sign in (d/dx)*cosh(x)=sinh(x)

---
 .../src/commonMain/kotlin/scientifik/kmath/misc/AutoDiff.kt     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/misc/AutoDiff.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/misc/AutoDiff.kt
index 3ff5fb557..8bc3f2936 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/misc/AutoDiff.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/misc/AutoDiff.kt
@@ -217,7 +217,7 @@ fun <T : Any, F : ExtendedField<T>> AutoDiffField<T, F>.sinh(x: Variable<T>): Va
     derive(variable { sin(x.value) }) { z -> x.d += z.d * cosh(x.value) }
 
 fun <T : Any, F : ExtendedField<T>> AutoDiffField<T, F>.cosh(x: Variable<T>): Variable<T> =
-    derive(variable { cos(x.value) }) { z -> x.d -= z.d * sinh(x.value) }
+    derive(variable { cos(x.value) }) { z -> x.d += z.d * sinh(x.value) }
 
 fun <T : Any, F : ExtendedField<T>> AutoDiffField<T, F>.tanh(x: Variable<T>): Variable<T> =
     derive(variable { tan(x.value) }) { z ->