How can I show that when r >> d, R1 - R2 is approximately equal to d cos theta? This was an intermediate step in my physics book when they derived some formula, and it just drives me crazy that I can't figure this out!
How can I show that when r >> d, R1 - R2 is approximately equal to d cos theta? This was an intermediate step in my physics book when they derived some formula, and it just drives me crazy that I can't figure this out!
Using the cosine rule for the triangle on the right hand side
And using the cosine rule on the triangle on the left side
cos180= -1, sin180=0
As r becomes much larger than d R1 and R2 become nearly equal to r