How do you differentiate #cos 2x#?

Question

↳Redirected from "An electron in a hydrogen atom drops from energy level n=5 to n=3. What is the energy transition using the Rydberg equation?"

8415 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-01-03T01:13:00

We let #y = cosu# and #u = 2x#. Then #dy/(du) = -sinu# and #(du)/dx= 2#.

#dy/dx = dy/(du) xx (du)/dx#

#dy/dx = -sinu xx 2#

#dy/dx = -2sinu#

Since #u = 2x#:

#dy/dx = -2sin2x#

Hopefully this helps!