Mrthfx

If I use the command PARENS{.....} with mtpro2 (green color into the figure in attachment) for to obtain a perfect brace curve (round bracket) I have 1 (one) problem:
the first and the second line of the fractions of the first equal are aligned and they have the same thick (you can see the two red rectangles).

But the line of the third fraction (green color) is not perfectly aligned with the previous fractions (infact two are below and the third is above) and the thick is different of the previous red fractions. To create a correct fraction with the two parens at the same distance with the command PARENS{.....}, using the package mtpro2, I have added a matrix, the command phantom{Z} and hspace{-.3cm} (you can see the green color).

Is there a different idea or solution to obtain of the perfect aligned fractions, with the same thick and perfect PARENS (...) (round brackets) so as when I use the command left(....right)?

documentclass[12pt]{book} 

usepackage{times} 

usepackage[lite]{mtpro2} 

usepackage{classico}

usepackage{mathtools}

begin{document}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

begin{equation}

begin{aligned}

overline F =frac{doverline p}{dt}&=\

&=frac{m}{sqrt{1-dfrac{u^2}{c^2}}}frac{doverline u}{dt}+moverline uPARENS{begin{matrix}phantom{Z}&\

dfrac{1}{sqrt{1-dfrac{u^2}{c^2}}} hspace{-.3cm}end{matrix}}=\

&=frac{m}{sqrt{1-dfrac{u^2}{c^2}}},overline a +frac{overline u}{c^2}frac{d}{dt}left(dfrac{mc^2}{sqrt{1-dfrac{u^2}{c^2}}}right)\

end{aligned}

end{equation}





end{document}

The thickness just appears to be different (probably due to how each pixel is rendered on screen). It should be fine if you print them out.

The PARENS command puts its content in a vcenter, thus, it will ignore the positioning of its baseline and the surrounding baseline. We can use some low-level box tricks to make the content symmetric with respect to the math axis, so that the two baselines are the same. The new command is called symmPARENS.

documentclass[12pt]{book}

usepackage{mathtools} % Load this early

%usepackage{times}

usepackage{newtxtext} % This is better :)

usepackage[lite]{mtpro2}



% Low-level hacks:

makeatletter

newsaveboxmtp@symm@box % The box to be made symmetric

% User level command:

newcommand*symmPARENS[1]{%

  setboxmtp@symm@boxhbox{$m@thdisplaystyle#1$}%

  dimen@dpmtp@symm@box

    advancedimen@fontdimen22textfonttw@ % dimen@ is the length from the math axis to the bottom

  dimen@iihtmtp@symm@box

    advancedimen@ii-fontdimen22textfonttw@ % dimen@ii is the length from the math axis to the top

  ifdimdimen@>dimen@ii

    advancedimen@fontdimen22textfonttw@

      htmtp@symm@boxdimen@ % Make mtp@symm@box higher

  else

    advancedimen@ii-fontdimen22textfonttw@

      dpmtp@symm@boxdimen@ii % Make mtp@symm@box deeper

  fi

  PARENS{copymtp@symm@box}%

}

makeatother



begin{document}

noindent

With verb|PARENS|, not so good:

begin{equation}

wbar{F} = frac{d wbar{p}}{dt}

  = frac{m}{sqrt{1-dfrac{u^2}{c^2}}} frac{d wbar{u}}{dt}

      + m wbar{u} PARENS{dfrac{1}{sqrt{1-dfrac{u^2}{c^2}}}}

end{equation}

With verb|symmPARENS|, centered, but not aesthetically pleasing:

begin{equation}

wbar{F} = frac{d wbar{p}}{dt}

  = frac{m}{sqrt{1-dfrac{u^2}{c^2}}} frac{d wbar{u}}{dt}

      + m wbar{u} symmPARENS{dfrac{1}{sqrt{1-dfrac{u^2}{c^2}}}}

end{equation}

Why not:

begin{equation}

wbar{F} = frac{d wbar{p}}{dt}

  = gamma m frac{d wbar{u}}{dt}

      + gamma m wbar{u},

 quad text{where } gamma = dfrac{1}{sqrt{1-dfrac{u^2}{c^2}}}

end{equation}

Please don't abuse verb|symmPARENS|:

begin{equation}

frac{1}{2} f(xi) = frac{1}{2} symmPARENS{frac{displaystyleint_a^b f(x) , dx}{b-a}}

text{ versus }

frac{1}{2} f(xi) = frac{1}{2} symmPARENS{frac{1}{b-a} displaystyleint_a^b f(x) , dx}

end{equation}

end{document}

Seriously, though, I would just write Eq. (3) instead.