WAEC - Mathematics (2011 - No. 14)
The perimeter of a sector of a circle of radius 4cm is (\(\pi + 8\))cm. Calculate the anle of the sector
45o
60o
75o
90o
Giải thích
Perimeter of sector = 2r + \(\frac{\theta}{360^o} \times 2\pi r\)
\(\pi + 8 = 2 \times 4 + \frac{\theta}{3360^o} \times 2 \pi \times 4\)
\(\pi + 8 + \frac{\theta}{360^o} \times 8 \pi\)
P + 8 - 8 = \(\frac{\theta \pi}{456o}\)
\(\pi = \frac{\theta \pi}{45^o}\)
\(\theta \pi = 45^o\)
\(\pi + 8 = 2 \times 4 + \frac{\theta}{3360^o} \times 2 \pi \times 4\)
\(\pi + 8 + \frac{\theta}{360^o} \times 8 \pi\)
P + 8 - 8 = \(\frac{\theta \pi}{456o}\)
\(\pi = \frac{\theta \pi}{45^o}\)
\(\theta \pi = 45^o\)