In the diagram, what is AC?

find the DB =[tex]\displaystyle\bf \sqrt{17^2-8^2} =15[/tex] ; now find AD=AB-DB=21-15=6 .Then AC=[tex]\displaystyle\bf \sqrt{AD^2+CD^2} =\sqrt{6^2+8^2} =10[/tex]
Answer:
C
Step-by-step explanation:
Using Pythagoras' identity in both right triangles
To find BD
BD² + CD² = BC²
BD² + 8² = 17²
BD² + 64 = 289 ( subtract 64 from both sides )
BD² = 225 ( take the square root of both sides )
BD = [tex]\sqrt{225}[/tex] = 15
Then
AD = AB - BD = 21 - 15 = 6
To find AC
AC² = AD² + CD²
AC² = 6² + 8² = 36 + 64 = 100 ( take the square root of both sides )
AC = [tex]\sqrt{100}[/tex] = 10 → C