tolong dibantu dengam caranya!

[tex]c = \sqrt{a^2 + b^2} \\ = \sqrt{20^2 + 15^2} \\ = \sqrt{400 + 225} \\ = \sqrt{625} \\ = 25[/tex]
L permukaan = 2L alas + L selimut
                      [tex]= 2 \frac{a. b}{2} + keliling segitiga. t \\ = a.b + (a + b + c)t \\ = 15.20 + (20 + 15 + 25)30 \\ = 300 + 60.30 \\ = 300 + 1800 \\ = 2100 cm^2[/tex]