Metallic ratios: Difference between revisions

m
used a bigger font to show the superscripts better (so as to aid readability), indented the formulas and centered the HTML table.
m (→‎{{header|REXX}}: added code when showing an EXACT value.)
m (used a bigger font to show the superscripts better (so as to aid readability), indented the formulas and centered the HTML table.)
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'''Metallic ratios''' are the real roots of the general form equation:
 
<big> x²<sup>2</sup> - bx - 1 = 0 </big>
 
where the integer '''b''' determines which specific one it is.
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Using the quadratic equation:
 
<big> ( -b ± √(b²<sup>2</sup> - 4ac) ) / 2a = x </big>
 
Substitute in (from the top equation) '''1''' for '''a''', '''-1''' for '''c''', and recognising that -b is negated we get:
 
<big> ( b ± √(b²<sup>2</sup> + 4) ) ) / 2 = x </big>
 
We only want the real root:
 
<big> ( b + √(b²<sup>2</sup> + 4) ) ) / 2 = x </big>
 
When we set '''b''' to '''1''', we get an irrational number: the '''Golden ratio'''.
 
<big> ( 1 + √(1²<sup>2</sup> + 4) ) / 2 = (1 + √5) / 2 = ~1.618033989... </big>
 
With '''b''' set to '''2''', we get a different irrational number: the '''Silver ratio'''.
 
<big> ( 2 + √(2²<sup>2</sup> + 4) ) / 2 = (2 + √8) / 2 = ~2.414213562... </big>
 
When the ratio '''b''' is '''3''', it is commonly referred to as the '''Bronze''' ratio, '''4''' and '''5'''
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'''Metallic ratios''' where '''b''' > '''0''' are also defined by the irrational continued fractions:
 
<big> [b;b,b,b,b,b,b,b,b,b,b,b,b,b,b,b,b...] </big>
 
 
So, The first 10ten '''Metallic ratios''' are:
 
:::::: {| class="wikitable" style="text-align: center;"
|+ Metallic ratios
!Name!!'''b'''!!Equation!!Value!!Continued fraction!!OEIS link