Question

Fara a se calcula sin15 si cos15 aratati ca
cos15-sin15=$\frac{ \sqrt{2} }{2}$

Answer 1

cos15 - sin15 = sin 75  - sin15  = 2 sin( 75  -15 )  / 2  · cos ( 75  + 15 ) /2 = 
= 2· sin 30 ·cos 45 =  2· 1 /2 ·√2 /2 = √2 /2

cos15 = sin( 90 -15 )