The lengths of the minor and major arcs 54cm and 126cm respectively. Calculate the angle of the major sector
A. 360o B. 252o C. 246o D. 234o
Correct Answer: B
Explanation
Let 0 = angle of the minor sector angle of the major sector = 360 - \(\theta\)(angle at a point) 2 \(\pi r\) = 54 + 126(i.e circumference of minor and major arc) 2\(\pi r = 180^o\) r = \(\frac{180}{2\pi}\) = \(\frac{90}{\pi}\) Lenght of ninor arc = \(\frac{\theta}{360} \times 2 \pi r\) 54 = \(\frac{\theta}{360} \times 3 \pi r\) \(\theta = \frac{360 \times 54}{2 \pi r}\) but r = \(\frac{90}{\pi}\) substituting \(\frac{90}{\pi}\) for r \(\theta = \frac{360 \times 54 \times \pi}{2 \times \pi \times 90}\) \(\theta = 2 \times 54 = 108^o\) angle of the major sector = 360 - 108o = 252o