Question

the expression cos (pi - x) is equivalent to

Answer 1

- cos(x)

Answer 2

thank you! can you explain how to got that?

Answer 3

Use the identity cos(x-y) = cos(x)cos(y) + sin(x)sin(y) to get...


cos(pi - x) = cos(pi)*cos(-x) + sin(pi)*sin(-x)


cos(pi - x) = cos(pi)*cos(x) - sin(pi)*sin(x)


cos(pi - x) = -1*cos(x) - 0*sin(x)


cos(pi - x) = -cos(x)

Answer 4

yes well u know it's a formula that cos(a-b)=cosa cosb+sina sinb

Answer 5

You also can think that on the unit circle the angle x and \(\pi-x\) are symmetric with respect to the y-axis, then \( \cos(\pi-x) =-\cos(x)\)