There are **16** NRICH Mathematical resources connected to **Sine rule & cosine rule**, you may find related items under Pythagoras and Trigonometry.

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Stick some cubes together to make a cuboid. Find two of the angles by as many different methods as you can devise.

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A hexagon, with sides alternately a and b units in length, is inscribed in a circle. How big is the radius of the circle?

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In a right-angled tetrahedron prove that the sum of the squares of the areas of the 3 faces in mutually perpendicular planes equals the square of the area of the sloping face. A generalisation. . . .

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Given a square ABCD of sides 10 cm, and using the corners as centres, construct four quadrants with radius 10 cm each inside the square. The four arcs intersect at P, Q, R and S. Find the. . . .

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Four rods are hinged at their ends to form a convex quadrilateral. Investigate the different shapes that the quadrilateral can take. Be patient this problem may be slow to load.

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If I tell you two sides of a right-angled triangle, you can easily work out the third. But what if the angle between the two sides is not a right angle?

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How far should the roof overhang to shade windows from the mid-day sun?

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Make and prove a conjecture about the cyclic quadrilateral inscribed in a circle of radius r that has the maximum perimeter and the maximum area.

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Find the sides of an equilateral triangle ABC where a trapezium BCPQ is drawn with BP=CQ=2 , PQ=1 and AP+AQ=sqrt7 . Note: there are 2 possible interpretations.

What is the shortest distance through the middle of a dodecahedron between the centres of two opposite faces?

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Re-arrange the pieces of the puzzle to form a rectangle and then to form an equilateral triangle. Calculate the angles and lengths.

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P is a point inside a square ABCD such that PA= 1, PB = 2 and PC = 3. How big is angle APB ?

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A white cross is placed symmetrically in a red disc with the central square of side length sqrt 2 and the arms of the cross of length 1 unit. What is the area of the disc still showing?

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Four rods are hinged at their ends to form a quadrilateral. How can you maximise its area?

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Three semi-circles have a common diameter, each touches the other two and two lie inside the biggest one. What is the radius of the circle that touches all three semi-circles?