There is a typo error, the perimeter of equilateral triangle ABC is 81/√3 centimeters.
Answer:
Radius = OB= 27 cm
Apothem = 13.5 cm
A diagram is attached for reference.
Step-by-step explanation:
Given,
The perimeter of equilateral triangle ABC is 81/√3 centimeters.
Substituting this in the formula of perimeter of equilateral triangle =
![=[tex]81\sqrt{3}](https://tex.z-dn.net/?f=%3D%5Btex%5D81%5Csqrt%7B3%7D)
![Side = \frac{81\sqrt{3} }{3} =27\sqrt{3} \ cm](https://tex.z-dn.net/?f=Side%20%3D%20%5Cfrac%7B81%5Csqrt%7B3%7D%20%7D%7B3%7D%20%3D27%5Csqrt%7B3%7D%20%5C%20cm)
Thus from the diagram , Side ![AB=BC=AC= 27\sqrt{3} \ cm](https://tex.z-dn.net/?f=AB%3DBC%3DAC%3D%2027%5Csqrt%7B3%7D%20%5C%20cm)
We know each angle of an equilateral triangle is 60°.
From the diagram, OB is an angle bisector.
Thus
°
Apothem is the line segment from the mid point of any side to the center the equilateral triangle.
Therefore considering ΔOBE, and applying tan function.
![tan\theta =\frac{perpendicular}{base} \\tan\theta=\frac{OE}{BE} \\tan\theta=\frac{OE}{\frac{27\sqrt{3}}{2} } \\tan30\times {\frac{27\sqrt{3} }{2} }= OE\\\frac{1}{\sqrt{3} } \times\frac{27\sqrt{3} }{2} =OE\\](https://tex.z-dn.net/?f=tan%5Ctheta%20%3D%5Cfrac%7Bperpendicular%7D%7Bbase%7D%20%5C%5Ctan%5Ctheta%3D%5Cfrac%7BOE%7D%7BBE%7D%20%5C%5Ctan%5Ctheta%3D%5Cfrac%7BOE%7D%7B%5Cfrac%7B27%5Csqrt%7B3%7D%7D%7B2%7D%20%20%7D%20%5C%5Ctan30%5Ctimes%20%7B%5Cfrac%7B27%5Csqrt%7B3%7D%20%7D%7B2%7D%20%7D%3D%20OE%5C%5C%5Cfrac%7B1%7D%7B%5Csqrt%7B3%7D%20%7D%20%5Ctimes%5Cfrac%7B27%5Csqrt%7B3%7D%20%7D%7B2%7D%20%3DOE%5C%5C)
Thus ,apothem OE= 13.5 cm
Now for radius,
We consider ΔOBE
![cos\theta=\frac{base}{hypotenuse} \\cos30= \frac{BE}{OB} \\Cos30 = \frac{\frac{27\sqrt{3} }{2}}{OB} \\OB= \frac{\frac{27\sqrt{3} }{2}}{cos30} \\OB= \frac{\frac{27\sqrt{3} }{2}}{\frac{\sqrt{3} }{2} } \\OB =27 \ cm](https://tex.z-dn.net/?f=cos%5Ctheta%3D%5Cfrac%7Bbase%7D%7Bhypotenuse%7D%20%5C%5Ccos30%3D%20%5Cfrac%7BBE%7D%7BOB%7D%20%5C%5CCos30%20%3D%20%5Cfrac%7B%5Cfrac%7B27%5Csqrt%7B3%7D%20%7D%7B2%7D%7D%7BOB%7D%20%20%5C%5COB%3D%20%5Cfrac%7B%5Cfrac%7B27%5Csqrt%7B3%7D%20%7D%7B2%7D%7D%7Bcos30%7D%20%5C%5COB%3D%20%5Cfrac%7B%5Cfrac%7B27%5Csqrt%7B3%7D%20%7D%7B2%7D%7D%7B%5Cfrac%7B%5Csqrt%7B3%7D%20%7D%7B2%7D%20%7D%20%5C%5COB%20%3D27%20%5C%20cm)
Thus for
Perimeter of equilateral triangle ABC is 81/√3 centimeters,
The radius of equilateral triangle ABC is 27 cm
The apothem of equilateral triangle ABC is 13.5 cm