as shown in figure LN = KN
triangle KLN is right angle triangle so using Pythagoras theorem
KL^2 = LN^2 + KN^2
KL^2 = LN^2 + LN^2 = 2LN^2
KL = √(2LN^2)
y = LN√2
now lets find value of LN
now LMN is also right angle triangle so using trigonometry
MN/LN = sin 30
putting value of MN=5 and sin 30 which is 1/2
5/LN = 1/2
LN = 5×2= 10
putting it back in our first equation
y = LN√2
y = 10√2