楼主:是BC=2吧?,就按BC=2计算此题目.
∠C=135,∠B=30,∠A=180-(∠C+∠B)=15.
sin15=sin(45-30)=sin45*cos30-cos45*sin30=√2/2*√3/2-√2/2*1/2=(√6-√2)/4.
BC=2,
BC/sin15=AC/sin30,
AC=BC*sin30/sin15=√6+√2.
AB/sin135=AC/sin30,
AB=AC*sin135/sin30=AC*sin45/sin30=2(√3+1).
楼主:是BC=2吧?,就按BC=2计算此题目.
∠C=135,∠B=30,∠A=180-(∠C+∠B)=15.
sin15=sin(45-30)=sin45*cos30-cos45*sin30=√2/2*√3/2-√2/2*1/2=(√6-√2)/4.
BC=2,
BC/sin15=AC/sin30,
AC=BC*sin30/sin15=√6+√2.
AB/sin135=AC/sin30,
AB=AC*sin135/sin30=AC*sin45/sin30=2(√3+1).