Question

Find the value of cos(-3π/4) in trigonometry ​

Answer 1

Answer:

Step-by-step explanation:

We have,

$\sf{cos\left(-\dfrac{3\pi}{4}\right)}$

$\sf{=cos\left(\dfrac{3\pi}{4}\right)}$

$\sf{=cos\left(\pi-\dfrac{\pi}{4}\right)}$

$\sf{=-cos\left(\dfrac{\pi}{4}\right)}$

$\sf{=-\dfrac{1}{\sqrt{2}}}$