Question 119385
The combined resistance of two resistors R1 and R2 in a
parallel circuit is given by the formula
Rt= 1 divided by 1/r1+1/r1 simplify the formula. 
:
Rt = {{{1/((1/r1) + (1/r2))}}}
:
Put the two fractions in denominator, over a single common denominator; (R1*R2)
Rt = {{{1/((r2+r1)/(r1*r2)))}}}
:
Invert the dividing fraction and multiply
Rt = 1 * {{{((r1*r2))/((r1+r2))}}}
Which is:
Rt = {{{((r1*r2))/((r1+r2))}}}
:
Did this bring it down to earth?