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How do you add two vectors using the triangle rule (head-to-tail)?

To add two vectors using the triangle rule, translate one vector so that its tail meets the head of the other. The sum vector is the arrow pointing from the initial start point of the first vector to the final endpoint of the second vector.

Conditions

  • Applicable to any planar or spatial vectors.
  • Vectors are treated as free vectors that can be translated.

Reasoning, step by step

  1. Identify the two vectors to be added.
  2. Translate the second vector so its start point coincides with the end point of the first vector.
  3. Draw a new vector from the start of the first vector to the end of the translated second vector.
  4. This new vector is the sum.

Example

The video shows translating AC to BD. Then AB→+BD→=AD→\overrightarrow{AB} + \overrightarrow{BD} = \overrightarrow{AD}. Since BD→=AC→\overrightarrow{BD} = \overrightarrow{AC}, this means AB→+AC→=AD→\overrightarrow{AB} + \overrightarrow{AC} = \overrightarrow{AD}.

Common misconceptions

  • Connecting the tails of both vectors instead of head-to-tail.
  • Forgetting that the sum vector points from the very first start to the very last end.

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.