Total differential to calculate approximately the largest error

[Ereisorhet]

I have the following problem:
Use the total differential to calculate approximately the largest error at determine the area of a triangle rectangle (right triangle) from the lengths of the cathetus if they measure 6 and 8 cm respectively, with a possible error of 0.1 cm for each measurement.

I did this:

 

[LCKurtz]

That is correct. I would have written it up a bit nicer. Something like this:
[MATH]A=\frac 1 2 bh[/MATH] so [MATH]dA = \frac 1 2(bdh + hdb) = \frac 1 2(6(\pm .1)+ 8(\pm .1))= \pm .3 \pm .4[/MATH]. So [MATH]|dA| \le .3 +.4 = .7[/MATH]