Question

answer this questions today is my exam yarrrrrrr plz

Answer 1

Find BD by pythagoras theorem for triangle ABD
Then subtract the answer from 21 as BC=21
Now you will get DC
again apply pythagoras theorem to triangle ACD
you will derive your answer

All the best!!

Answer 2

We have
AD = 8cm
AC = x cm
DC = 1/2BC
= 1/2×21
= 10.5

According to pythagoras theorem

(AD)^2 +(DC)^2 = (AC)^2
(8)^2 + (10.5)^2 =AC^2
64 + 110.25 = Ac^2
174.25 =AC^2
13.20 = AC
13.20=X

Hence the value of x is 13.20