Routines
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37AA: THE 'COSINE' FUNCTION (offset +20)
 The address of this routine is found in the table of addresses. It is called via the calculator literal +20 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 37AA RST \$28 X 37AB DEFB \$39 get_argt: V 37AC DEFB \$2A abs: ABS V 37AD DEFB \$A1 stk_one: ABS V, 1 37AE DEFB \$03 subtract: ABS V-1 37AF DEFB \$E0 get_mem_0: ABS V-1, (1/0) 37B0 DEFB \$00 jump_true to C_ENT: ABS V-1=W 37B1 DEFB \$06 If the jump was not made then continue. 37B2 DEFB \$1B negate: 1-ABS V 37B3 DEFB \$33 jump to C_ENT: 1-ABS V=W 37B4 DEFB \$03
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