解：如圖，?$∠C=∠E=90°，$??$∠A=60°，$??$∠B=30°，$??$∠D=∠F=45°$?
∴?$AB=2AC，$??$DE=EF$?
∴?$BC=\sqrt {AB^2-AC^2}=\sqrt 3AC，$??$DF=\sqrt {DE^2+EF^2}=\sqrt 2DF$?
∴?$sin 60°=sinA=\frac {BC}{AB}=\frac {\sqrt 3}2，$??$cos 60°=cosA=\frac {AC}{AB}=\frac 12$?
?$tan 60°=tan A=\frac {BC}{AC}=\sqrt 3$?
?$sin 30°=sinB=\frac {AC}{AB}=\frac 12，$??$cos 30°=cosB=\frac {BC}{AB}=\frac {\sqrt 3}2$?
?$tan 30°=tanB=\frac {AC}{BC}=\frac {\sqrt 3}3$?
?$sin 45°=sinD=\frac {EF}{DF}=\frac {\sqrt 2}2，$??$cos 45°=cosD=\frac {DE}{DF}=\frac {\sqrt 2}2$?
?$tan 45°=tan D=\frac {EF}{DE}=1$?
