Question:medium
Einthoven's law is best expressed as:
Einthoven's law is best expressed as:
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In Einthoven's triangle, lead II equals lead I plus lead III.
Updated On: Jun 24, 2026
- I + III = II
- I - III = II
- I + II + III = 0
- I + III = aVL
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Picture Einthoven's triangle, an equilateral arrangement of leads I, II and III around the heart, each measuring a potential difference between two limb electrodes.
Step 2: Because these three leads are vectors arranged in a closed triangle, their instantaneous potentials are linked by a fixed algebraic relationship rather than being independent of one another.
Step 3: Once the polarity of each lead is taken into account, lead II turns out to equal lead I added to lead III. Symbolically this is $I + III = II$, which is the statement of Einthoven's law and lets you compute any missing lead from the other two.
Step 4: Comparing the choices, only $I + III = II$ matches this relationship, so it is the correct expression.
\[\boxed{I + III = II}\]
Step 2: Because these three leads are vectors arranged in a closed triangle, their instantaneous potentials are linked by a fixed algebraic relationship rather than being independent of one another.
Step 3: Once the polarity of each lead is taken into account, lead II turns out to equal lead I added to lead III. Symbolically this is $I + III = II$, which is the statement of Einthoven's law and lets you compute any missing lead from the other two.
Step 4: Comparing the choices, only $I + III = II$ matches this relationship, so it is the correct expression.
\[\boxed{I + III = II}\]
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