Answer number 1 please.

[tex] \sf {a}^{2} = {13}^{2} - {5}^{2} [/tex]
Formula :
Base²= Hypotenuse² - Perpendicular ²
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[tex] \hookrightarrow\sf {a}^{2} = {13}^{2} - {5}^{2} [/tex]
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[tex] \hookrightarrow\sf {a}^{2} =169 - 25[/tex]
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[tex] \hookrightarrow\sf {a}^{2} =144[/tex]
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[tex] \hookrightarrow\sf {a} = \sqrt{144} [/tex]
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[tex] \hookrightarrow\sf {a} = \sqrt{12 \times 12} [/tex]
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[tex] \hookrightarrow\sf {a} = 12[/tex]
Remember the a² in formula has nothing to do with the a we have to find. :)
[tex]\bold{\huge{\pink{\underline{ Solution }}}}[/tex]
[tex]\bold{\underline{ Given :-}}[/tex]
[tex]\bold{\underline{ Let's\: Begin:-}}[/tex]
That is,
[tex]\sf{\red{ ( Base)² + ( Perpendicular )² = ( Hypotenuse)²}}[/tex]
[tex]\sf{ ( a )² + ( b )² = ( c )²}[/tex]
Subsitute the required values,
[tex]\sf{ ( a )² + ( 5 )² = ( 13)²}[/tex]
[tex]\sf{ a² + 25 = 169}[/tex]
[tex]\sf{ a² = 169 - 25 }[/tex]
[tex]\sf{ a² = 144}[/tex]
[tex]\sf{ a = √144}[/tex]
[tex]\sf{ a = 12}[/tex]
[tex]\sf{\blue{ Hence,\: Length \:of \:a\: is \:12 units }}[/tex]