Question

If cos θ = 4/5, what is cos (- θ)?

Answer 1

\[\cos (- \theta)=\cos(\theta)= 4/5\]\[\theta \]

Answer 2

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

Answer 3

just for 4/5

Answer 4

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

Answer 5

ohkay so it would be cos(- θ)= 4/5?

Answer 6

Try drawing the two triangles on a coordinate grid.

Answer 7

ohkay, im not sure how that helps me?

Answer 8

Do you know what the definition of cosine is?

Answer 9

no

Answer 10

cos(-theta)=cos theta

Answer 11

so then its just 4/5

Answer 12

yep!!!

Answer 13

thanks!!