# Question #366e9

##### 2 Answers

Feb 2, 2018

#### Explanation:

start with the sum and difference formulas for sine:

add them together to get:

For this problem, let

Feb 2, 2018

#### Explanation:

#"using the "color(blue)"product to sum formula"#

#â€¢color(white)(x)2sinAcosB=sin(A+B)+sin(A-B)#

#"here "A=7theta" and "B=3theta#

#rArr2sin7thetacos3theta#

#=sin(7theta+3theta)+sin(7theta-3theta)#

#=sin10theta+sin4theta#