Răspuns:
Explicație pas cu pas:
sin 15°=sin (45°-30°)=sin 45cos30-cos45sin 30=
=√3/2×√2/2-√2/4=√2/4(√3-1)
sin 15°=AB/BC AB=12×√2/4(√3-1)=3√2(√3-1) cm
AC=BC cos 15
cos15°=cos(45°-30°)=cos45cos30+sin 45sin30=√2/2×√3/2+√2/2×1.2=
=√2/4(√3+1)
AC=12√2/4(√3+1)=√2/4(√3+1)cm
P=√2/4(√3+1)+√2/4(√3-1) +12=2√2/4√3=√6/2 cm
A=√2/4(√3+1)×√2/4(√3-1)/2=(3-1)/4=1/2=0,5 cm²
