nilai dari [tex] \frac{ \sin(105) - \sin(15) }{ \cos(75) - \cos(15) } [/tex]

sin(105)=sin(90+15)= cos15
cos(75)=cos(90-15)= sin15
cos(15)=1/4(√6+√2)
sin(15)=1/4(√6-√2)
cos15-sin15=(1/2)√2
sin15-cos15= -(1/2)√2
(cos15-sin15)/(sin15-cos15)=-1