# Precalculus Examples

,

The equation for finding the angle between two vectors states that the dot product of the two vectors equals the product of the magnitudes of the vectors and the cosine of the angle between them.

Solve the equation for .

To find the dot product, find the sum of the products of corresponding components of the vectors.

Substitute the components of the vectors into the expression.

Simplify.

Remove parentheses.

Simplify each term.

Multiply by to get .

Multiply by to get .

Add and to get .

To find the magnitude of the vector, find the square root of the sum of the components of the vector squared.

Substitute the components of the vector into the expression.

Simplify.

Raise to the power of to get .

Remove parentheses around .

Raise to the power of to get .

Add and to get .

Rewrite as .

Factor out of .

Rewrite as .

Pull terms out from under the radical.

To find the magnitude of the vector, find the square root of the sum of the components of the vector squared.

Substitute the components of the vector into the expression.

Simplify.

Remove parentheses around .

Raise to the power of to get .

Remove parentheses around .

Raise to the power of to get .

Add and to get .

Rewrite as .

Factor out of .

Rewrite as .

Pull terms out from under the radical.

Substitute the values into the equation for the angle between the vectors.

Simplify terms.

Multiply by to get .

Remove parentheses around .

Reduce the expression by cancelling the common factors.

Move .

Cancel the common factor.

Rewrite the expression.

Reduce the expression by cancelling the common factors.

Move .

Cancel the common factor.

Rewrite the expression.

Combine using the product rule for radicals.

Simplify the denominator.

Multiply by to get .

Rewrite as .

Pull terms out from under the radical.

Reduce the expression by cancelling the common factors.

Cancel the common factor.

Rewrite the expression.

Multiply by .

Simplify.

Combine.

Raise to the power of .

Raise to the power of .

Use the power rule to combine exponents.

Add and to get .

Rewrite as .

Multiply by to get .

Evaluate to get .