Answer: X = 7√2
Explanation:
Let first Consider triangle BDC,
Cos C = adjacent/ hypothenus
Cos C = 7 / x ...... (1)
Also, let consider triangle ABC
Cos C = adjacent / hypothenus
Cos C = x / 14 ....... (2)
Since angle C is the same, equate equation 1 to 2
7/ x = x / 14
Cross multiply
X^2 = 98
Make x the subject of formula
X = sqrt (98)
X = sqrt ( 49 × 2 )
X = sqrt (49) × sqrt (2)
X = 7 sqrt(2)
X = 7√2