diff --git a/src/app/dialogs/tools/dialogarc.cpp b/src/app/dialogs/tools/dialogarc.cpp
index b0ba3332b..31671ed08 100644
--- a/src/app/dialogs/tools/dialogarc.cpp
+++ b/src/app/dialogs/tools/dialogarc.cpp
@@ -45,8 +45,9 @@
  */
 DialogArc::DialogArc(const VContainer *data, const quint32 &toolId, QWidget *parent)
     :DialogTool(data, toolId, parent), ui(new Ui::DialogArc), flagRadius(false), flagF1(false), flagF2(false),
-      timerRadius(nullptr), timerF1(nullptr), timerF2(nullptr), center(NULL_ID), radius(QString()), f1(QString()),
-      f2(QString()), formulaBaseHeight(0), formulaBaseHeightF1(0), formulaBaseHeightF2(0), path(nullptr)
+      timerRadius(nullptr), timerF1(nullptr), timerF2(nullptr), center(NULL_ID), radius(QString()),
+      f1(QString()), f2(QString()), formulaBaseHeight(0), formulaBaseHeightF1(0), formulaBaseHeightF2(0), path(nullptr),
+      angleF1(0), angleF2(0)
 {
     ui->setupUi(this);
 
@@ -65,10 +66,10 @@ DialogArc::DialogArc(const VContainer *data, const quint32 &toolId, QWidget *par
     connect(timerRadius, &QTimer::timeout, this, &DialogArc::EvalRadius);
 
     timerF1 = new QTimer(this);
-    connect(timerF1, &QTimer::timeout, this, &DialogArc::EvalF1);
+    connect(timerF1, &QTimer::timeout, this, &DialogArc::EvalF);
 
     timerF2 = new QTimer(this);
-    connect(timerF2, &QTimer::timeout, this, &DialogArc::EvalF2);
+    connect(timerF2, &QTimer::timeout, this, &DialogArc::EvalF);
 
     InitOkCancelApply(ui);
 
@@ -81,8 +82,8 @@ DialogArc::DialogArc(const VContainer *data, const quint32 &toolId, QWidget *par
     connect(ui->toolButtonPutHereF2, &QPushButton::clicked, this, &DialogArc::PutF2);
 
     connect(ui->toolButtonEqualRadius, &QPushButton::clicked, this, &DialogArc::EvalRadius);
-    connect(ui->toolButtonEqualF1, &QPushButton::clicked, this, &DialogArc::EvalF1);
-    connect(ui->toolButtonEqualF2, &QPushButton::clicked, this, &DialogArc::EvalF2);
+    connect(ui->toolButtonEqualF1, &QPushButton::clicked, this, &DialogArc::EvalF);
+    connect(ui->toolButtonEqualF2, &QPushButton::clicked, this, &DialogArc::EvalF);
 
     connect(ui->plainTextEditFormula, &QPlainTextEdit::textChanged, this, &DialogArc::RadiusChanged);
     connect(ui->plainTextEditF1, &QPlainTextEdit::textChanged, this, &DialogArc::F1Changed);
@@ -356,22 +357,17 @@ void DialogArc::EvalRadius()
 
 //---------------------------------------------------------------------------------------------------------------------
 /**
- * @brief EvalF1 calculate value of first angle
+ * @brief EvalF1 calculate value of angle
  */
-void DialogArc::EvalF1()
+void DialogArc::EvalF()
 {
     labelEditFormula = ui->labelEditF1;
-    Eval(ui->plainTextEditF1->toPlainText(), flagF1, ui->labelResultF1, degreeSymbol, false);
-}
+    angleF1 = Eval(ui->plainTextEditF1->toPlainText(), flagF1, ui->labelResultF1, degreeSymbol, false);
 
-//---------------------------------------------------------------------------------------------------------------------
-/**
- * @brief EvalF2 calculate value of second angle
- */
-void DialogArc::EvalF2()
-{
     labelEditFormula = ui->labelEditF2;
-    Eval(ui->plainTextEditF2->toPlainText(), flagF2, ui->labelResultF2, degreeSymbol, false);
+    angleF2 = Eval(ui->plainTextEditF2->toPlainText(), flagF2, ui->labelResultF2, degreeSymbol, false);
+
+    CheckAngles();
 }
 
 //---------------------------------------------------------------------------------------------------------------------
@@ -394,3 +390,20 @@ void DialogArc::ShowLineAngles()
     }
     ui->listWidget->setCurrentRow (0);
 }
+
+//---------------------------------------------------------------------------------------------------------------------
+void DialogArc::CheckAngles()
+{
+    if (qFuzzyCompare(angleF1 + 1, angleF2 + 1))
+    {
+        flagF1 = false;
+        ChangeColor(ui->labelEditF1, Qt::red);
+        ui->labelResultF1->setToolTip(tr("Angles equal"));
+
+        flagF2 = false;
+        ChangeColor(ui->labelEditF2, Qt::red);
+        ui->labelResultF2->setToolTip(tr("Angles equal"));
+    }
+
+    DialogArc::CheckState();
+}
diff --git a/src/app/dialogs/tools/dialogarc.h b/src/app/dialogs/tools/dialogarc.h
index 823d7f69f..b042268ea 100644
--- a/src/app/dialogs/tools/dialogarc.h
+++ b/src/app/dialogs/tools/dialogarc.h
@@ -126,11 +126,13 @@ private:
 
     VisToolArc    *path;
 
-    void          EvalRadius();
-    void          EvalF1();
-    void          EvalF2();
-    void          ShowLineAngles();
+    qreal         angleF1;
+    qreal         angleF2;
 
+    void          EvalRadius();
+    void          EvalF();
+    void          ShowLineAngles();
+    void          CheckAngles();
 };
 
 //---------------------------------------------------------------------------------------------------------------------
diff --git a/src/app/dialogs/tools/dialogtool.cpp b/src/app/dialogs/tools/dialogtool.cpp
index dca1e7965..e5942bc19 100644
--- a/src/app/dialogs/tools/dialogtool.cpp
+++ b/src/app/dialogs/tools/dialogtool.cpp
@@ -473,10 +473,13 @@ void DialogTool::ValFormulaChanged(bool &flag, QPlainTextEdit *edit, QTimer *tim
  * @param postfix unit name
  * @param checkZero true - if formula can't be equal zero
  */
-void DialogTool::Eval(const QString &text, bool &flag, QLabel *label, const QString& postfix, bool checkZero)
+qreal DialogTool::Eval(const QString &text, bool &flag, QLabel *label, const QString& postfix, bool checkZero)
 {
     SCASSERT(label != nullptr);
     SCASSERT(labelEditFormula != nullptr);
+
+    qreal result = 0;
+
     if (text.isEmpty())
     {
         flag = false;
@@ -493,7 +496,7 @@ void DialogTool::Eval(const QString &text, bool &flag, QLabel *label, const QStr
             formula.replace("\n", " ");
             formula = qApp->FormulaFromUser(formula);
             Calculator *cal = new Calculator(data);
-            const qreal result = cal->EvalFormula(formula);
+            result = cal->EvalFormula(formula);
             delete cal;
 
             //if result equal 0
@@ -537,6 +540,7 @@ void DialogTool::Eval(const QString &text, bool &flag, QLabel *label, const QStr
         }
     }
     CheckState();
+    return result;
 }
 
 //---------------------------------------------------------------------------------------------------------------------
diff --git a/src/app/dialogs/tools/dialogtool.h b/src/app/dialogs/tools/dialogtool.h
index 0cf27043d..32e76d892 100644
--- a/src/app/dialogs/tools/dialogtool.h
+++ b/src/app/dialogs/tools/dialogtool.h
@@ -225,7 +225,7 @@ protected:
     void             PutValHere(QPlainTextEdit *plainTextEdit, QListWidget *listWidget);
     void             ValFormulaChanged(bool &flag, QLineEdit *edit, QTimer * timer);
     void             ValFormulaChanged(bool &flag, QPlainTextEdit *edit, QTimer * timer);
-    void             Eval(const QString &text, bool &flag, QLabel *label, const QString &postfix,
+    qreal            Eval(const QString &text, bool &flag, QLabel *label, const QString &postfix,
                           bool checkZero = true);
     void             setCurrentPointId(QComboBox *box, quint32 &pointId, const quint32 &value) const;
     void             setCurrentSplineId(QComboBox *box, quint32 &splineId, const quint32 &value,