livethelifewelove Group Title If cos θ = 4/5, what is cos (- θ)? 2 years ago 2 years ago

1. ipm1988

$\cos (- \theta)=\cos(\theta)= 4/5$$\theta$

2. livethelifewelove

yeah i know you switch it, but now do I just plug that in my calculator or leave it?

3. ipm1988

just for 4/5

4. CliffSedge

cosine is even function, f(-x) = f(x)

5. livethelifewelove

ohkay so it would be cos(- θ)= 4/5?

6. CliffSedge

Try drawing the two triangles on a coordinate grid. |dw:1349313476943:dw|

7. livethelifewelove

ohkay, im not sure how that helps me?

8. CliffSedge

Do you know what the definition of cosine is?

9. livethelifewelove

no

10. AravindG

cos(-theta)=cos theta

11. livethelifewelove

so then its just 4/5

12. AravindG

yep!!!

13. livethelifewelove

thanks!!