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First published on Thursday, Jan 9, 2025 and last modified on Thursday, Jan 9, 2025

Linear Algebra in the Euclidian Space: Section 7 test

Fabienne Chaplais Mathedu

Keywords: Polar Coordinates, Rotation

1 The Table of Trigonometry

For the use of the test, we give you the table of the cosine and sine of some angles in Radian.

Figure 1

2 Question 1: Calculate the polar coordinates of the vector with cartesian coordinates \( x_{1}=2\) and \( y_{1}=2\)

Denote \( \overrightarrow{u}_{1}\) that vector, and calculate successively:

  1. The norm \( R_{1}\) of \( \overrightarrow{u}_{1}\) .

    Use the formula \( \sqrt{p^{2}q}=p\sqrt{q}\) for \( p\) and \( q\) positive integers.

  2. The cosine \( \cos(\theta_{1})\) of the polar angle of \( \overrightarrow{u}_{1}\) .

    Simplify the fraction and use the formula \( \frac{p}{\sqrt{q}}=\frac{p\sqrt{q}}{q}\) for \( p\) and \( q\) positive integers.

  3. The sine \( \sin(\theta_{1})\) of the polar angle of \( \overrightarrow{u}_{1}\) .

    Simplify the fraction and use the formula \( \frac{p}{\sqrt{q}}=\frac{p\sqrt{q}}{q}\) for \( p\) and \( q\) positive integers.

  4. The polar angle \( \theta_{1}\) of \( \overrightarrow{u}_{1}\) .

    Use the table 1.

3 Question 2: Calculate the polar coordinates of the vector with cartesian coordinates \( x_{2}=-\sqrt{3}\) and \( y_{2}=1\)

Denote \( \overrightarrow{u}_{2}\) that vector, and calculate successively:

  1. The norm \( R_{2}\) of \( \overrightarrow{u}_{2}\) .

  2. The cosine \( \cos(\theta_{2})\) of the polar angle of \( \overrightarrow{u}_{2}\) .

  3. The sine \( \sin(\theta_{2})\) of the polar angle of \( \overrightarrow{u}_{2}\) .

  4. The polar angle \( \theta_{2}\) of \( \overrightarrow{u}_{2}\) .

    Use the table 1.

4 Question 3: Calculate the angle \( \theta\) between the two vectors defined in questions 1 and 2

4.1 Solution