The isosceles triangle has a base that measures 14 units. the value of y, the length of each leg, must be
equal to 7.
between 7 and 14.
greater than 7.
between 14 and 28.

Draw a median to the base. 

x = 7/cosy 

where , y angle between leg and base
x: leg

7 is half length of base.

x = 7/cosy

For cosy only positve (as leg length can only be a positive value) 

1 > |cosy| > 0  flip all sides

1 < 1/cosy < infinity    multiply times 7  

7 < 7/cosy < infinity

7/cosy = x

7 < x < infinity

To make that more discrete:

at cosy = cos 0 = 1

x = 7/1 = 7 (minimum) 

at cosy = cos60 = 0.5

x = 7/0.5 =14

at cosy = cos89 = 0.017

x = 7/0.017 = 401

but at cosy = cos90 = 0

x = 7/0 = infinity  (max point)

check the number line attached. 

greater than 7 

P0000000000p genafhysjq each e yeh wy