Vectors

Step 1: Formula for angle between two vectors.
The angle between two vectors and is given by the formula: where is the dot product of the vectors and and are the magnitudes of the vectors.

Step 2: Calculating the dot product.
The dot product is:

Step 3: Calculating the magnitudes.
The magnitudes of and are:

Step 4: Finding the angle.
Now, using the formula for the angle:

Step 5: Conclusion.
Thus, the angle between the vectors is 60°, which makes the statement true.

Step 1: Understanding the vector sum.
The sum of the three sides of a triangle taken in order gives a vector sum of zero, since the triangle is a closed figure.

Step 2: Conclusion.
Thus, the vector sum of the three sides of a triangle taken in order is zero.