5.21.24 Rewrite an expression with different options : convert convertir
convert takes two arguments an expression and an option.
convert rewrites this expression applying rules depending
on the option. Valid options are :

sin converts an expression like trigsin.
 cos converts an expression like trigcos.
 sincos converts an expression like sincos.
 trig converts an expression like sincos.
 tan converts an expression like halftan.
 exp converts an expression like trig2exp.
 ln converts an expression like trig2exp.
 expln converts an expression like trig2exp.
 string converts an expression into a string.
 matrix converts a list of lists into a matrix.
 polynom converts a Taylor series into a polynomial
by removing the remainder (cf 5.25.22).
 parfrac or partfrac or fullparfrac converts a rational
fraction into its partial fraction decomposition (5.29.9).
convert can also :

convert units, for example
convert(1000_g,_kg)=1.0_kg (cf 8.1.4).
 write a real as a continued fraction :
convert(a,confrac,’fc’) writes a as a continued fraction
stored in fc. Do not forget to quote the last argument if it
was assigned.
For example, convert(1.2,confrac,’fc’)=[1,5] and fc contains the
continued fraction equal to 1.2 (cf 5.8.7).
 transform an integer into the list of its digits in a
base, beginning with the units digit (and reciprocally)

convert(n,base,b) transforms the integer n into the list of its
digits in base b beginning with the units digit.
For example,
convert(123,base,10)=[3,2,1] and reciprocally
 convert(l,base,b) transforms the list l into the integer n
which has l as list of its
digits in base b beginning with the units digit.
For example,
convert([3,2,1],base,10)=123 (cf 5.5).