Which

Which of the following numbers most accurately area of a regular decagon with side s = 2 cm?

(A) 9.51 cm2
(B) 20 cm2
(C) 30.78 cm2
(D) 31.84 cm2
(E) 32.90 cm2

Result

S =  30.7768
x = (Correct answer is: C) Wrong answer

Step-by-step explanation:

n=10 a=2  α=2π2 n=2 3.14162 100.3142  tanα=a/2:h h=a/2/tan(α)=2/2/tan(0.3142)3.0777  S1=a h2=2 3.077723.0777  S=n S1=10 3.0777=30.7768
x=C



Did you find an error or inaccuracy? Feel free to write us. Thank you!



avatar







Tips to related online calculators
See also our right triangle calculator.
See also our trigonometric triangle calculator.

 
We encourage you to watch this tutorial video on this math problem: video1

Related math problems and questions:

  • Decagon prism
    10gon A regular decagon of side a = 2 cm is the base of the perpendicular prism, the side walls are squares. Find the prism volume in cm3, round to two decimal places.
  • Regular 5-gon
    5gon Calculate the area of the regular pentagon with side 7 cm.
  • Triangles
    triangles Find out whether given sizes of the angles can be interior angles of a triangle: a) 23°10',84°30',72°20' b) 90°,41°33',48°37' c) 14°51',90°,75°49' d) 58°58',59°59',60°3'
  • Triangle SAS
    triangle_iron Calculate the triangle area and perimeter, if the two sides are 51 cm and 110 cm long and angle them clamped is 130 °.
  • Find the
    12gon Find the content of a regular 12 sided polygon if its side a = 12 cm.
  • Reverse Pythagorean theorem
    pytagors Given are lengths of the sides of the triangles. Decide which one is rectangular: Δ ABC: 77 dm, 85 dm, 36 dm ... Δ DEF: 55 dm, 82 dm, 61 dm ... Δ GHI: 24 mm, 25 mm, 7 mm ... Δ JKL: 32 dm, 51 dm, 82 dm ... Δ MNO: 51 dm, 45 dm,
  • Right triangle Alef
    r_triangle The obvod of a right triangle is 84 cm, and the hypotenuse is 37 cm long. Determine the lengths of the legs.
  • Glass
    pohgar How many glass are needed to produce glass with base regular 5-gon if one base triangle in the base is 4.2 square cm and the height is 10 cm?
  • Bricks pyramid
    The_Great_Pyramid How many 50cm x 32cm x 30cm brick needed to built a 272m x 272m x 278m pyramid?
  • Regular n-gon
    regular_polygons Which regular polygon have a radius of circumscribed circle r = 10 cm and the radius of inscribed circle p = 9.962 cm?
  • 30-gon
    30gon At a regular 30-gon the radius of the inscribed circle is 15cm. Find the "a" side size, circle radius "R", circumference, and content area.
  • Calculate
    triangle_ssh Calculate the area of triangle ABC, if given by alpha = 49°, beta = 31°, and the height on the c side is 9cm.
  • Parallelogram +ľ
    rovnobeznik | AB | = 76cm, | BC | = 44cm, angle BAD = 30 °. Find the area of the parallelogram.
  • Hexagon A
    hexagon Calculate area of regular hexagon inscribed in circle with radius r=9 cm.
  • Triangle - is RT?
    triangle_3_angles Triangle has a circumference of 90 cm. Side b is 1 cm longer than c, and side c is 31 cm longer than side a. Calculate the length of sides and determine whether a triangle is a right triangle.
  • Triangle ABC v2
    triangles Area of the triangle is 12 cm square. Angle ACB = 30º , AC = (x + 2) cm, BC = x cm. Calculate the value of x.
  • Juice box 2
    pfanner-ananas Box with juice has the shape of a cuboid. Internal dimensions are 15 cm, 20 cm, and 32 cm. Suppose the box stays at the smallest base juice level reaches 4 cm below the upper base. How much internal volume of the box fills juice? How many cm below the bas