diff --git a/basic/sources/commands/base/clear.asm b/basic/sources/commands/base/clear.asm
index d3e04ada..47345741 100644
--- a/basic/sources/commands/base/clear.asm
+++ b/basic/sources/commands/base/clear.asm
@@ -100,6 +100,14 @@ ClearCodeSetMemoryA:
 		.DoSendMessage 					
 		.byte 	10,1
 		.DoWaitMessage		
+		;
+		; 		Reset to Degrees
+		;
+		lda 	#1
+		sta 	ControlParameters+0
+		.DoSendMessage 					
+		.byte 	4,35
+		.DoWaitMessage		
 		ply
 		rts
 
diff --git a/basic/test.bsc b/basic/test.bsc
index 4c4810b3..afdadcdc 100644
--- a/basic/test.bsc
+++ b/basic/test.bsc
@@ -1 +1,24 @@
-10 print 1.2
+
+while peek($FF00):wend
+poke $FF04,0
+poke $FF01,35
+poke $FF00,4
+while peek($FF00):wend
+
+a = 3.1415/4
+s = sin(a)
+t = tan(a)
+print a;" ";s;" ";t;" ";atan(t)
+print
+
+while peek($FF00):wend
+poke $FF04,1
+poke $FF01,35
+poke $FF00,4
+while peek($FF00):wend
+
+a = 45
+s = sin(a)
+t = tan(a)
+print a;" ";s;" ";t;" ";atan(t)
+
diff --git a/documents/release/source/api.tex b/documents/release/source/api.tex
index 9f2273c2..5b3561a6 100644
--- a/documents/release/source/api.tex
+++ b/documents/release/source/api.tex
@@ -22,7 +22,7 @@
 
 \title{Neo6502 Assembly - Messaging API}
 \author{Paul Robson \\ Bill Auger}
-\date{2024-04-03}
+\date{2024-04-04}
 
 \renewcommand{\familydefault}{\sfdefault}
 \graphicspath{ {./img/}                             % WRT local editor (eg: texworks)
@@ -750,16 +750,16 @@ \section{API Functions}\label{api-functions}
 Register1 := square root(Register 1)
 }
 \ApiFnRow{19}{Sine}{
-Register1 := sine(Register 1) angles in degrees
+Register1 := sine(Register 1) angles in degrees/radians
 }
 \ApiFnRow{20}{Cosine}{
-Register1 := cosine(Register 1) angles in degrees
+Register1 := cosine(Register 1) angles in degrees/radians
 }
 \ApiFnRow{21}{Tangent}{
-Register1 := tangent(Register 1) angles in degrees
+Register1 := tangent(Register 1) angles in degrees/radians
 }
 \ApiFnRow{22}{Arctangent}{
-Register1 := arctangent(Register 1) angles in degrees
+Register1 := arctangent(Register 1) angles in degrees/radians
 }
 \ApiFnRow{23}{Exponent}{
 Register1 :=  e to the power of Register 1
@@ -788,6 +788,9 @@ \section{API Functions}\label{api-functions}
 \ApiFnRow{34}{Number to String}{
 Convert the constant in Register1 to a length prefixed string which is stored at \Param{4,5}
 }
+\ApiFnRow{35}{Set Degree/Radian Mode}{
+Sets the use of degrees (the default) when non zero, radians when zero.
+}
 \end{longtable*}
 \pagebreak
 \begin{longtable*}{ | c | l | p{12cm} | }
diff --git a/firmware/common/config/defines.inc b/firmware/common/config/defines.inc
deleted file mode 100644
index 519e04e6..00000000
--- a/firmware/common/config/defines.inc
+++ /dev/null
@@ -1,2 +0,0 @@
-#define FROMRADIANS(n) ((n) * 180.0 / M_PI)
-#define TORADIANS(n)   ((n) * M_PI / 180.0)
diff --git a/firmware/common/config/dispatch.config b/firmware/common/config/dispatch.config
index 45d415ee..3517d8c5 100644
--- a/firmware/common/config/dispatch.config
+++ b/firmware/common/config/dispatch.config
@@ -10,8 +10,6 @@
 // ***************************************************************************************
 // ***************************************************************************************
 
-include defines.inc
-
 include system/group1_system.inc
 include display/group2_console.inc
 include system/group3_fileio.inc
diff --git a/firmware/common/config/mathematics/group4_other.inc b/firmware/common/config/mathematics/group4_other.inc
index 2ed8f4bf..ee774901 100644
--- a/firmware/common/config/mathematics/group4_other.inc
+++ b/firmware/common/config/mathematics/group4_other.inc
@@ -26,3 +26,9 @@
 		MATHConvertNumberToString(DCOMMAND);
 	DOCUMENTATION
 		Convert the constant in Register1 to a length prefixed string which is stored at \Param{4,5}
+
+	FUNCTION 35 Set Degree/Radian Mode
+		MATHSetAngleMeasure(DPARAMS[0] != 0);
+	DOCUMENTATION
+		Sets the use of degrees (the default) when non zero, radians when zero.
+
diff --git a/firmware/common/config/mathematics/group4_unary.inc b/firmware/common/config/mathematics/group4_unary.inc
index 553656c7..85df49ed 100644
--- a/firmware/common/config/mathematics/group4_unary.inc
+++ b/firmware/common/config/mathematics/group4_unary.inc
@@ -41,27 +41,27 @@
 
 	FUNCTION 19 Sine
 		f1 = MATHReadFloat(MATH_REG1);
-		MATHWriteFloat(sin(TORADIANS(f1)),MATH_REG1);
+		MATHWriteFloat(sin(MATHConvertAngleToDefault(f1)),MATH_REG1);
 	DOCUMENTATION
-		Register1 := sine(Register 1) angles in degrees
+		Register1 := sine(Register 1) angles in degrees/radians
 
 	FUNCTION 20 Cosine
 		f1 = MATHReadFloat(MATH_REG1);
-		MATHWriteFloat(cos(TORADIANS(f1)),MATH_REG1);
+		MATHWriteFloat(cos(MATHConvertAngleToDefault(f1)),MATH_REG1);
 	DOCUMENTATION
-		Register1 := cosine(Register 1) angles in degrees
+		Register1 := cosine(Register 1) angles in degrees/radians
 
 	FUNCTION 21 Tangent
 		f1 = MATHReadFloat(MATH_REG1);
-		MATHWriteFloat(tan(TORADIANS(f1)),MATH_REG1);
+		MATHWriteFloat(tan(MATHConvertAngleToDefault(f1)),MATH_REG1);
 	DOCUMENTATION
-		Register1 := tangent(Register 1) angles in degrees
+		Register1 := tangent(Register 1) angles in degrees/radians
 
 	FUNCTION 22 Arctangent
 		f1 = MATHReadFloat(MATH_REG1);
-		MATHWriteFloat(FROMRADIANS(atan(f1)),MATH_REG1);
+		MATHWriteFloat(MATHConvertAngleFromDefault(atan(f1)),MATH_REG1);
 	DOCUMENTATION
-		Register1 := arctangent(Register 1) angles in degrees
+		Register1 := arctangent(Register 1) angles in degrees/radians
 
 	FUNCTION 23 Exponent
 		f1 = MATHReadFloat(MATH_REG1);
diff --git a/firmware/common/include/interface/maths.h b/firmware/common/include/interface/maths.h
index 11da5a16..35928908 100644
--- a/firmware/common/include/interface/maths.h
+++ b/firmware/common/include/interface/maths.h
@@ -28,6 +28,10 @@ void MATHProcessDecimal(uint8_t *command);
 void MATHConvertStringToNumber(uint8_t *command);
 void MATHConvertNumberToString(uint8_t *command);
 
+float MATHConvertAngleToDefault(float angle);
+float MATHConvertAngleFromDefault(float angle);
+void MATHSetAngleMeasure(bool bDegrees);
+
 #endif
 
 // ***************************************************************************************
diff --git a/firmware/common/sources/interface/maths.cpp b/firmware/common/sources/interface/maths.cpp
index 503da94c..33b1c145 100644
--- a/firmware/common/sources/interface/maths.cpp
+++ b/firmware/common/sources/interface/maths.cpp
@@ -32,11 +32,34 @@ static union _regConvert {
 	uint32_t i;
 } sc;
 
+//
+//		Degrees / Radians flag.
+//
+static bool bUseDegrees = true;
+
 //
 //		Map offset to actual register start address (Placeholder)
 //
 #define REGADDR(ofst) (regAddress+(ofst))
 
+// ***************************************************************************************
+//
+//								Handle degrees and radians
+//
+// ***************************************************************************************
+
+float MATHConvertAngleToDefault(float angle) {
+	return bUseDegrees ? angle * M_PI / 180.0 : angle;
+}
+
+float MATHConvertAngleFromDefault(float angle) {
+	return bUseDegrees ? angle * 180.0 / M_PI : angle;
+}
+
+void MATHSetAngleMeasure(bool bDegrees) {
+	bUseDegrees = bDegrees;
+}
+
 // ***************************************************************************************
 //
 //			Read a register 1/2 into the conversion structure, returns control byte