Use the trapezium rule with four ordinates (three strips) to find an approximate value for
$$\int _ { 1.5 } ^ { 6 } x ^ { 2 } \sqrt { x ^ { 2 } - 1 } \mathrm {~d} x$$
giving your answer to three significant figures.
State how you could obtain a better approximation to the value of the integral using the trapezium rule.
(1 mark)