### Home > A2C > Chapter 8 > Lesson 8.1.4 > Problem8-67

8-67.

Consider the system of equations $y = \cos x$ and $y = −1$.

1. Is it possible to solve this system by substitution? By the Elimination Method? By graphing?

Use substitution: $cos\left(x\right) = −1$. Solve for $x$.

2. List at least five possible solutions.

List five values where the graphs intersect.

3. Consider the list of solutions you wrote in part (b) as a sequence and write a rule to represent all possible solutions.

List your values from part (b) in order and look for a relationship.

$x = \left(−180 + 360n\right)^\circ$ for all integers $n$

Use the eTool below to help answer parts (a) and (b).
Click the link at right for the full version of the eTool: CCA2 7-66 HW eTool