This figure is incorrect, as it indicates that sin ( a ) + sin ( b ) = sin ( a + b 2 ) {\displaystyle \sin(a)+\sin(b)=\sin \left({\frac {a+b}{2}}\right)} and cos ( a ) + cos ( b ) = cos ( a + b 2 ) {\displaystyle \cos(a)+\cos(b)=\cos \left({\frac {a+b}{2}}\right)} , which is not true. However, sin ( a ) + sin ( b ) cos ( a ) + cos ( b ) = sin ( a + b 2 ) cos ( a + b 2 ) {\displaystyle {\frac {\sin(a)+\sin(b)}{\cos(a)+\cos(b)}}={\frac {\displaystyle \sin \left({\frac {a+b}{2}}\right)}{\displaystyle \cos \left({\frac {a+b}{2}}\right)}}} . —Kri (talk) 22:38, 19 September 2024 (UTC)[reply]
