Formula for resistance in parallel circuit

[DB]

My science teacher gave me this formula for resistance in parallel circuit.
$$\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+...$$

Thats exactly how he wrote it.
I would like this using the summation sigma

$$\frac{1}{R_{eq}}=\sum_{R=\frac{1}{R_n}}^n$$

Is that right? I am sure it's not lol...

 

[ZapperZ]

My science teacher gave me this formula for resistance in parallel circuit.
$$\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+...$$

Thats exactly how he wrote it.
I would like this using the summation sigma

$$\frac{1}{R_{eq}}=\sum_{R=\frac{1}{R_n}}^n$$

Is that right? I am sure it's not lol...

Not quite. You should write it as

$$\frac{1}{R_{eq}}=\sum_{i=1}}^n \frac{1}{R_i}$$

Zz.

 

[Crosson]

$$\frac{1}{R_{eq}}=\sum_{i=1}^n \frac{1}{R_i}$$

Where n is the number of resistors and i is just a dummy letter (a counter).