As we can see that the given triangle is a right triangle and one other angle is also given which is 25 degrees , Now the side opposite to angle 25 degrees is called as Opposite , and the side adjacent to 25 degrees angle is called Adjacent
Now , Opposite = 10
And
Adjacent = x
and angle = 25 degrees
Now the trigonometric ratio which relates these three things is tan
[tex] tan( 25 )= \frac{opposite}{adjacent} = \frac{10}{x} [/tex]
[tex] tan(25) = \frac{10}{x} [/tex]
Multiply both sides by x
x * tan(25) = 10
Divide both sides by tan(25) , and use calculator we get
[tex] x=\frac{10}{tan(25) } = 21.445 [/tex]
x= 21.445
Hence Option B , 21.4 is the correct answer
