A ship sails 6 kilometres north and then 8 kilometres east. How far is it from the harbour? The distance sailed is one number, but where the ship is needs a size and a direction. In this course you describe a vector by its components and its direction cosines, add and scale vectors, and find the point that divides a line in a given ratio. It covers the first part of the Indian syllabus unit (NCERT, JEE Main) and the matching topics of A-Level, IB and AP.
3 lessons, about 1 h 20 min3 simulations10 problems3 practice questionsPython in every lesson
A vector has a size and a direction. We write it with components along the three axes, find its magnitude with the theorem of Pythagoras, and divide by the magnitude to get a unit vector. The direction cosines are the components of that unit vector.
Vectors add by the triangle law or the parallelogram law, and in components we add the matching components. Multiplying by a number stretches or flips a vector. The vector from a point to a point is found as the position vector of minus the position vector of .
A point that divides a line segment in the ratio has the position vector . The same formula, with replaced by , gives the point that divides the segment externally. The midpoint, the centroid and the fourth vertex of a parallelogram all follow from it.
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