### Home > INT3 > Chapter 12 > Lesson 12.2.3 > Problem 12-110

12-110.

Show how to derive the double angle formulas for sin(2*x*) and cos(2*x*) by substituting *x* for both *α* and *β* in the formulas for sin(*α* + *β*) and cos(*α* + *β*), then simplifying. Homework Help ✎

sin(*x* + *x*)

What is this equivalent to? How can you change it?

sin(*x* + *x*) = sin(*x*)cos(*x*) + cos(*x*)sin(*x*) = 2sin(*x*)cos(*x*)

Now use the same method to find the the double angle formula for cos(2*x*).