trouble reading sin graph, not accurate anymore?

my problem is that though I am aware i can use Rsin(x-a) to express this equation **i never get the same answers as the book which uses Rcos(x+a).** The book chose to express the equation as Rcos(x+a), however i want to express it as Rsin(x-a) because i am unable to read off the sin graph, it does not work anymore the reading are inaccurate.** Can someone represent the equation as Rsin(x-a) and tell me how they got there?**

__the books R(cos.. working__

the equation

this results in a=73.74