given:
ST=1/2 (SR)
SR=a (diameter)
hint: draw QT
=>ST=1/2 (a)=a/2 (radius)
then we know that SQ=a/2 and QT=a/2
=> triangle SQT is an equilateral triangle, so all angles are equal and each measures 45°
a. m (ST)
Length of the arc (ST)= 2πr(theta/360°)
in your case r=a/2
(ST)=2π(a/2)(45°/360°)
(ST)=(2r*π)/8=(r*π)/4
(ST)=(a*π/2)/4
(ST)=(a*π)/8
b. m (TR)=circumference/2-ST= 2π-(a*π)/8=π (16 - a)/8
c. m (STR)=circumference/2 =(2(a/2)π)/2=(aπ)/2
answers:
a. m (ST)= (a*π)/8
b. m (TR)=π (16 - a)/8
c. m (STR)=(aπ)/2
d. m (S)= 45°