nilai dari cos 15°-cos105° / sin 15°-sin75°

cos(15)-cos(105)=cos(15)-cos(90+15)=cos(15)-(-sin(15))=cos(15)+sin(15)

sin(15)-sin(75)=sin(15)-sin(90-15)=sin(15)-cos(15)

[tex]\frac{\cos{15}+\sin{15}}{\sin{15}-\cos{15}}\times \frac{\sin{15}+\cos{15}}{\sin{15}+\cos{15}}=\frac{\sin^{2}{15}+\cos^{2}{15}+2\sin{15}\cos{15}}{\sin^{2}{15}-\cos^{2}{15}}\\=\frac{1+\sin{30}}{-\cos{30}}\\=-\frac{\frac{3}{2}}{\frac{\sqrt{3}}{2}}\\=-\frac{3}{\sqrt{3}}\\=-\sqrt{3}[/tex]