** Final Answer

**

** Step-by-step Solution **

** Specify the solving method

**

**

The cosine of $135$ equals $-\frac{\sqrt{2}}{2}$

Learn how to solve trigonometric equations problems step by step online.

$-\frac{\sqrt{2}}{2}=4\cos\left(\right)$

Learn how to solve trigonometric equations problems step by step online. Solve the equation cos(135)=4cos(). The cosine of 135 equals -\frac{\sqrt{2}}{2}. The cosine of 315 equals \frac{\sqrt{2}}{2}. Multiply -3 times \frac{\sqrt{2}}{2}. Subtract the values 45 and -2.121321.

** Final Answer

**