Find the exact value of sin²75°, given that sin15° = (√3 -1)/2√2.

Could someone please explain to me the relevance of sin15° in finding sin²75°?

Thanx

Printable View

- October 7th 2008, 01:11 AMxwrathbringerxExact Value - Please Help?!
Find the exact value of sin²75°, given that sin15° = (√3 -1)/2√2.

Could someone please explain to me the relevance of sin15° in finding sin²75°?

Thanx - October 7th 2008, 01:18 AMGreengoblin
presumably you are expected to know that and

- October 7th 2008, 01:20 AMxwrathbringerx
errr sori but that's made me more confused (Worried)

- October 7th 2008, 02:08 AMGreengoblin
Sorry, whats confusing you? often you are expected to memorize the sin and cosine of some comon angles, such as etc.

The fomula is for the sine of the sum of two angles. Have you seen this yet? I just realised you don't have the cosines of the angles anyway, so probably you have to draw a diagram, label the sides of the triangles, and remember - October 7th 2008, 02:13 AMxwrathbringerx
oh i get it ...how stupid of me

thanx