[填空题]
Let Q=$\frac{(sin2x+b)(2sinx-1)}{a^2-4tanx}$,where x =45$^{\circ}$. a=18 and b =$\sqrt{2}$.
1.Find the exact value of Q.
Q= .
2.Give your answer to part (a) correct to
2.1.three decimal places;
The number is .
2.2.three significant figures.
The number is .
3.Calculate the percentage error if Q is given to three decimal places.
Using the percentage error formula ϵ= %
