Tolong ya kak... Ini maksudnya gimana?

2.
[tex] ac \: = \sqrt{15^{2} + 15 ^{2} } \\ = \sqrt{225 + 225 } \\ = \sqrt{450} \\ = \sqrt{15 {}^{2} \times 2} \\ = 15 \sqrt{2} [/tex]
[tex]bh = \sqrt{15 ^{2} +(15 \sqrt{ 2} {}^{}) ^{2} } \\ = \sqrt{225 + (225 \times 2)} \\ = \sqrt{225 + 450} \\ = \sqrt{675} \\ = 15 \sqrt{3} [/tex]
3.
[tex]af = \sqrt{5 {}^{2} + 12 {}^{2} } \\ = \sqrt{25 + 144} \\ = \sqrt{169 } \\ = 13[/tex]