# 1เลือกประเภทtan(60°−30°)=x\tan\left(60\degree-30\degree\right)=xtan(60°−30°)=xx=tan60°−tan30°1−tan60°tan30°x=\frac{\tan60\degree-\tan30\degree}{1-\tan60\degree\tan30\degree}x=1−tan60°tan30°tan60°−tan30°x=tan60°−tan30°2+tan60°tan30°x=\frac{\tan60\degree-\tan30\degree}{2+\tan60\degree\tan30\degree}x=2+tan60°tan30°tan60°−tan30°x=tan30°−tan30°1+tan60°tan60°x=\frac{\tan30\degree-\tan30\degree}{1+\tan60\degree\tan60\degree}x=1+tan60°tan60°tan30°−tan30°x=tan60°−tan30°1+tan60°tan30°x=\frac{\tan60\degree-\tan30\degree}{1+\tan60\degree\tan30\degree}x=1+tan60°tan30°tan60°−tan30°
# 2เลือกประเภทsin140°cos250°+sin70°cos320°=x\sin140\degree\cos250\degree+\sin70\degree\cos320\degree=xsin140°cos250°+sin70°cos320°=xx=sin(70°+40°)x=\sin\left(70\degree+40\degree\right)x=sin(70°+40°)x=sin30°x=\sin30\degreex=sin30°x=cos(70°−40°)x=\cos\left(70\degree-40\degree\right)x=cos(70°−40°)x=cos30°x=\cos30\degreex=cos30°
# 3เลือกประเภทtanA−tanB1+tanAtanB\frac{\tan A-\tan B}{1+\tan A\tan B}1+tanAtanBtanA−tanB โดยA=123°,B=93° A=123\degree,B=93\degreeA=123°,B=93° จงหา cot(A−B)\cot\left(A-B\right)cot(A−B)1tan(123°−93°)\frac{1}{\tan\left(123\degree-93\degree\right)}tan(123°−93°)11tan(93°−123°)\frac{1}{\tan\left(93\degree-123\degree\right)}tan(93°−123°)1cot(93°+123°)\cot\left(93\degree+123\degree\right)cot(93°+123°)cos(93°+123°)\cos\left(93\degree+123\degree\right)cos(93°+123°)
# 4OXcsc(70°−40°)=1sin(70°−40°)=12\csc\left(70\degree-40\degree\right)=\frac{1}{\sin\left(70\degree-40\degree\right)}=\frac12csc(70°−40°)=sin(70°−40°)1=21