Evaluate \(\frac{0.8 \times 0.43 \times 0.031}{0.05 \times 0.72 \times 0.021}\). Correct to four significant figures.

An arc subtends an angle of 30^o at the centre of a circle radius 12cm. Calculate the length of the arc.

Evaluate \(\int\limits_0^\frac{\pi}{2}\) sin xdx

An arc of the length 16\(\pi\)cm subtends an angle of 80^o at the centre of the circle. Find the radius of the circle.