A circle has a chord that goes from ( pi)/8 π8 to (4 pi) / 3 4π3 radians on the circle. If the area of the circle is 75 pi 75π, what is the length of the chord?
1 Answer
Sep 7, 2017
Explanation:
"calculate the length of the chord using the "color(blue)"cosine rule"calculate the length of the chord using the cosine rule
color(red)(bar(ul(|color(white)(2/2)color(black)(c^2=a^2+b^2-(2abcosC)color(white)(2/2)|)))
"where c is the length of the chord, a and b are the radii"
"and C is the angle subtended at the centre of the circle"
"by the chord"
pir^2=75pilarr" area of circle"
rArrr^2=75rArrr=+-sqrt75=5sqrt3
angleC=(4pi)/3-pi/8=(32pi)/24-(3pi)/24=(29pi)/24
c^2=(5sqrt3)^2+(5sqrt3)^2-(2xx5sqrt3xx5sqrt3xxcos((29pi)/24))
color(white)(c^2)=75+75-(-119)=269
rArrc=sqrt269~~ 16.4" units"