prisma triunghiulara regulata are in baza un triunghi echilateral
P=3a;15=3a⇒a=5 cm
[tex] A_{t} =2 A_{b}+ A_{l}=2* \frac{a^2 \sqrt{3} }{4}+P*h=2* \frac{25 \sqrt{3} }{4}+15*7= \\ = \frac{25 \sqrt{3} }{2}+105(cm^2) \\ V= A_{b}*h = \frac{25 \sqrt{3} }{4}*7= \frac{175 \sqrt{3} }{4}(cm^3) [/tex]
