Answer:
[tex]a = 5[/tex]
Step-by-step explanation:
Notice that [tex]\triangle CDB[/tex] is a right triangle where its hypotenuse is [tex]\overline{CB}[/tex]. We can also see that [tex]a = CB[/tex]. For this we must use the Pythagorean Theorem.
Recall:
The Pythagorean Theorem states that if you have a right triangle, the principal square root of the sum of the squares of each leg is the length the hypotenuse.
We can see that [tex]CD = 3[/tex] and [tex]DB = 4[/tex]
[tex]a = \sqrt{CD^2 +DB^2} \\ a = \sqrt{3^2 +4^2} \\ a = \sqrt{9 +16} \\ a = \sqrt{25} \\ a = 5[/tex]
