[left] Is your CHDK uBasic without Trig. functions?
Pasting a couple of subroutines can end that era.

Here are two small routines that you can incorporate into your own program. Just copy and paste a few lines and add your input and deal with the output. Both scripts indicate a suitable magnitude of input and a format for printing output. Degree is the preferred angle unit but radians are available.
The two scripts are independent of each other, if you use them together ensure the variables do not unintentionally transfer values. CHDK Integers have a range +/- 2^31 (2E9) DO NOT overflow!

SIN (Sindeg.bas)
Ref: http://lab.polygonal.de/2007/07/18/fast-and-accurate-sinecosine-approximation/
Registered under Open Source Initiative - MIT License
Copy & Paste to your program the "SIN" subroutine between the rem---------------- lines.
Input d=205 will calculate Sin (20.5)deg. as 3500 (representing 0.3500)
The input range is 0 -> 900 (+90 deg.), small angles use the approximation Sin(x) = x radian
larger angles use the ELSE ~~~~~ ENDIF section. A two stage process 1st approximation and then a refinement. The maximum output is 9999 (representing +1).
COS(c) may be calculated by using (c = 900-d) eg c = 900-205 will output Cos(69.5) ~ 3500
TAN(t) may be calculated by using TAN(t) = SIN(t)/COS(t), COS(t) replaced by SIN(900-t)
ie two runs SIN(c) then SIN(900-t) take care when dividing the result to obtain TAN or you will lose some significant digits. The correct sign for for other quadrants may need to be considered.

ArcTAN (Atansub.bas)
ArcTAN(x) means, calculate the angle whose TANgent is x
Ref: Stuart Ball www.lightsoft.co.uk/PDstu/stuchat#37.html (#36 gives additional detail)
Copy & Paste to your program "ATAN" subroutine between the rem ---------------- lines.
Input x=456 (0.456) and the script will calculate the angle which has that value of TAN in degree and radian (24.4d, 0.43r).
Ex. 'A4' sheet as landscape height = 210, width = 297. Calculate angle of diagonal.
uBasic 210/297 ? hence scale factor of 1000 required. NB! Angle is relative to denominator (the bottom #)
Calculate 210 * 1000 / 297 = 707. chdkArcTAN(707)= 352. Interpret as 35.2deg to 297 direction.
Now 'A4' as portrait Calculate 297 * 1000/210 = 1414. chdkArcTAN = ### -> 54.7deg to 210 direction.
The low input range is -999 to +999 corresponding to angles of -45 deg to +45 deg respectively.
mid input range is 1000 > 3161 corresponds to angles 45 to 72 and
hi input range 3162>9999 will output about 72 to 84 deg.

The approximations used have appeared on web discussion pages but only seem to get rare exposure.
The ArcTAN was refined by Prof. Ranko Bojanic (who has given me a licence to use his formula without any rescrictions). An earlier ref: Approximation Theory (C. Hastings, Jr., Note 143, Math. Tables Aids. Comp 6, 68 (1953)) gave K as 0.28
An alternative to the above method is to use Atanlo only and rotate into the required quadrant.
I've adapted both to use integer calculation, both are quick, use a small amount of memory and are fairly accurate. After all this is a camera!

[/left]

[b]SIN[/b]
rem Parabolic Sine Approximation
rem For explanation of method visit url
rem [url=http://lab.polygonal.de/2007/07/18/fast-and-accurate-sinecosine-approximation/]polygonal labs » Fast and accurate sine/cosine approximation[/url]
rem features 1/10 degree as input, output 1/10000, accuracy varies about 1/1000 
rem deg/180 = rad/pi, sine < 10deg ~ rad 
rem used variables d,r,s,k,p,q,i
rem rad= deg*pi/180 ~ 'deg*3500/2034
rem 1st approx.  s= 4d/180(1-d/180)
rem refined by q= 225/1000*((s*s) - s) + s


s=0
for i = 5 to 50 step 10
d=i*15 +3
gosub "sin"
next i
end

rem ------------------------------------------------------
:sin
if d < 100 then
 	 r= d*3550/2034
	 print "Sine(",d/10,".",d %10,")  = 0. 0",r 
	
else
	s= (1800-d)*4/18*d/18
rem  refinement	 
	k=s/40*9
	p=s-10000
	q=p/100*k/100
rem	print "d,r,Sine,q ",d,r,s,q
	print  "Sine(",d/10,".",d %10,") = 0.",q+s
endif
return
rem -----------------------------------------------------

SINE approx. compared to Calculator
Camera approximation Calculator
Sine( 7 . 8 ) = 0. 136 0.1357
Sine( 22 . 8 ) = 0. 3876 0.3875
Sine( 37 . 8 ) = 0. 6146 0.6129
Sine( 52 . 8 ) = 0. 7957 0.7965
Sine( 67 . 8 ) = 0. 9253 0.9258

[b]ARCTAN[/b]
rem uBasic ArcTan Integer Approximation  
rem ref: url [url=http://www.lightsoft.co.uk/PDstu/stuchat#37.html]www.lightsoft.co.uk/PDstu/stuchat#37.html[/url]
rem Author Aged on S3is with UB Debugger 
rem Licence and approximation by Ranko Bojanic
rem K=0.280872 ~ 116/413. 180/pi/100 ~ 2034/3550
rem for |x| <= 1, Arctan(x)  ~ x/(1+K*x^2) ~ 45deg
rem for x>1, Arctan(x) ~ 90 - (x/x^2+K)*180/pi)
rem for x >3.162 Arctan (x) ~ 90 -1/x *180/pi ~ 72deg

rem Lo Input:- range (x)  -1,1  max 1000, Output:-   10ths degee
rem accuracy varies 1/1000 approx. See print out and ref
rem used variables x,d,r,a
d=0
r=0
a=0


for x=-753 to 9500 step 543
gosub "atan"
next x
end


	rem ----------------------------------------------------------------
:atan
rem print "x =",x
if x <= 999 then gosub "atanlo"
if x > 1000 and x< 3162 then gosub "atanmid"
if x>3162 then gosub "atanhi"
return
	
:atanlo
	d = (x*x*116/413) 
	d=d/100+10000
	r=100000*x/d
	a=r*2034/3550
rem	print "Atan x<1 d r a ",x,d,r,a
 if x<= 999 then print " Atan( .",x%1000, " ) ~  Rad .",r/10, " ~  Deg ",a/100,".",a%100
return

:atanmid
	d=x*x/100+2809
	r=x*10000/d
	a=r*2034/3550
rem	print "d>1 x d r a",x,d,r,900-a
	 print " Atan(",x, ")  ~  Deg ",(900-a)/10,".",(900-a)%10
return

:atanhi
	r=572958/x
	a=900-r
rem	print "d>3 x  r a",x,r,a
	print " Atan(",x/1000, "." x-x/1000*1000")  ~  Deg ",(a)/10,".",(a)%10
return

rem ----------------------------------------------------------------

Annotated output
Atansub.bas
input Camera approximation x Range Calculator
>>> Atan( . -753 ) ~ Rad . -649 ~ Deg -37 . -21 ¦ -1<x<=1 -36.9
>>> Atan( . -210 ) ~ Rad . -207 ~ Deg -11 . -88 ¦ atanlo -11.86
>>> Atan( . 333 ) ~ Rad . 322 ~ Deg 18 . 50 ¦ " +18.41
>>> Atan( . 876 ) ~ Rad . 720 ~ Deg 41 . 28 ¦ -1<x<=1 +41.22
>>> Atan( 1419 ) ~ Deg 54 . 6 ¦ 1<x<3 + 54.8
>>> Atan( 1962 ) ~ Deg 62 . 8 ¦ atanmid 62.9
>>> Atan( 2505 ) ~ Deg 68 . 2 ¦ " 68.2
>>> Atan( 3048 ) ~ Deg 71 . 8 ¦ 1<x<3+ 71.8
>>> Atan( 3 .591) ~ Deg 74 . 1 ¦ 3+<x<10 74.1
>>> Atan( 4 .134) ~ Deg 76 . 2 ¦ atanhi 76.4
>>> Atan( 5 .763) ~ Deg 80 . 1 ¦ " 80.1
>>> Atan( 7 .392) ~ Deg 82 . 3 ¦ " 82.3
>>> Atan( 9 .21) ~ Deg 83 . 7 ¦ 3+<x<10 83.8