Spectrum ROM: Routine at 14250

The address of this routine is found in the table of addresses. It is called via the calculator literal 32 by the routines at DRAW and tan. It is also called indirectly via fp_calc_2.

This subroutine handles the function COS X and returns a 'last value' 'that is an approximation to COS X.

The subroutine uses the expression COS X=SIN (πW/2), where -1<=W<=1.

In deriving W for X the subroutine uses the test result obtained in the previous subroutine and stored for this purpose in mem-0. It then jumps to the sin subroutine, entering at C_ENT, to produce a 'last value' of COS X.

The address of this routine is found in the table of addresses. It is called via the calculator literal 32 by the routines at DRAW and tan. It is also called indirectly via fp_calc_2. This subroutine handles the function COS X and returns a 'last value' 'that is an approximation to COS X. The subroutine uses the expression COS X=SIN (πW/2), where -1<=W<=1. In deriving W for X the subroutine uses the test result obtained in the previous subroutine and stored for this purpose in mem-0. It then jumps to the sin subroutine, entering at C_ENT, to produce a 'last value' of COS X.
cos	14250	RST 40	X
	14251	DEFB 57	get_argt: V
	14252	DEFB 42	abs: ABS V
	14253	DEFB 161	stk_one: ABS V, 1
	14254	DEFB 3	subtract: ABS V-1
	14255	DEFB 224	get_mem_0: ABS V-1, (1/0)
	14256	DEFB 0	jump_true to C_ENT: ABS V-1=W
	14257	DEFB 6	jump_true to C_ENT: ABS V-1=W
If the jump was not made then continue.
	14258	DEFB 27	negate: 1-ABS V
	14259	DEFB 51	jump to C_ENT: 1-ABS V=W
	14260	DEFB 3	jump to C_ENT: 1-ABS V=W