trig help

sin (a°+ b°) = sin a° cos b° + sin b° cos a°

Find the value of sin 75° (w/o calc/graphs)

Not too worried about the answer but just how to get it. Thanks in advance.

 

75 = 45 + 30

sin (45+30) = sin 45 cos 30 + sin 30 cos 45

That's what you're trying to get at, right?

 

and just sub in special triangles?, i think i got it now, thanks

 

Yea. Like knowing that the sides of a 45/45/90 triangle are 1,1,2^(1/2) and a 30/60/90 is 1,2,3^(1/2) you can substitute your known sin and cos values.

 

my class was recently doing the same thing and we used trig properties to reduce the equation. I would have to go look them up if that would help at all.