Exercise 36 Page 119

We have been asked to find m∠ DOB. The expression m∠ DOB is the angle measure between the rays OD and OB.

The sum of m∠ BOC and m∠ COD is equal to m∠ DOB. m∠ BOC+ m∠ COD= m∠ DOB

m∠ BOC +m∠ COD = m∠ DOB

SubstituteII

m∠ AOB= 20, m∠ BOC= 45

20+ 45=m∠ DOB

AddTerms

Add terms

65=m∠ DOB

RearrangeEqn

Rearrange equation

m∠ DOB= 65