you are given height=6
look at that
a right triangle
legs 2 and 6
a^2+b^2=c^2
2^2+6^2=c^2
4+36=c^2
40=c^2
sqrt both sides
2√10=c
the other one
legs 3 and 6
3^2+6^2=c^2
9+36=c^2
45=c^2
3√5=c
the legnth of the side on the left is 3√5
lefnth of side on righ tis 2√10