Sine, cosine, tangent

  • Pythagoras on a Sphere
    problem

    Pythagoras on a sphere

    Age
    16 to 18
    Challenge level
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    Prove Pythagoras' Theorem for right-angled spherical triangles.
  • Over The Pole
    problem

    Over the pole

    Age
    16 to 18
    Challenge level
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    Two places are diametrically opposite each other on the same line of latitude. Compare the distances between them travelling along the line of latitude and travelling over the nearest pole.
  • Dodecawhat
    problem

    Dodecawhat

    Age
    14 to 16
    Challenge level
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    Follow instructions to fold sheets of A4 paper into pentagons and assemble them to form a dodecahedron. Calculate the error in the angle of the not perfectly regular pentagons you make.

  • Where is the dot?
    problem

    Where is the dot?

    Age
    14 to 16
    Challenge level
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    A dot starts at the point (1,0) and turns anticlockwise. Can you estimate the height of the dot after it has turned through 45 degrees? Can you calculate its height?

  • Doesn't add up
    problem

    Doesn't add up

    Age
    14 to 16
    Challenge level
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    In this problem we are faced with an apparently easy area problem, but it has gone horribly wrong! What happened?

  • Inscribed in a Circle
    problem

    Inscribed in a circle

    Age
    14 to 16
    Challenge level
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    The area of a square inscribed in a circle with a unit radius is 2. What is the area of these other regular polygons inscribed in a circle with a unit radius?

  • Moving Squares
    problem

    Moving squares

    Age
    14 to 16
    Challenge level
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    How can you represent the curvature of a cylinder on a flat piece of paper?
  • Cosines Rule
    problem

    Cosines rule

    Age
    14 to 16
    Challenge level
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    Three points A, B and C lie in this order on a line, and P is any point in the plane. Use the Cosine Rule to prove the following statement.

  • Six Discs
    problem

    Six discs

    Age
    14 to 16
    Challenge level
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    Six circular discs are packed in different-shaped boxes so that the discs touch their neighbours and the sides of the box. Can you put the boxes in order according to the areas of their bases?
  • Far Horizon
    problem

    Far horizon

    Age
    14 to 16
    Challenge level
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    An observer is on top of a lighthouse. How far from the foot of the lighthouse is the horizon that the observer can see?