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Olympiad 3

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2. cos A + cos B + cos C = 4 sin A 2 sin B 2 sin C 2<br />

3. tan A + tan B + tan C = tan A tan B tan C<br />

4. tan A 2 tan B 2 + tan A 2 tan C 2 + tan B 2 tan C 2 = 1<br />

Exercise 22. ABCD is a quadrilateral<br />

whose diagonals intersect at O.<br />

If ∠AOB = 30 ◦ , AC = 24 cm and<br />

BD = 22 cm, find the area of ABCD.<br />

B<br />

A<br />

30 ◦<br />

O<br />

D<br />

C<br />

Exercise 23. In the figure, ABCDEF is a regular hexagon with area equal<br />

to 3 √ 3 cm 2 . Find the area of the square P QRS.<br />

Q<br />

C<br />

B<br />

P<br />

D<br />

A<br />

R<br />

E<br />

F<br />

S<br />

Exercise 24. ABCD is a square,<br />

AEF is a n isosceles triangle, and<br />

∠EAF = 30 ◦ . Points E and F lie on<br />

BC and CD respectively. The area of<br />

△AEF is 1. Find the area of ABCD.<br />

D<br />

30 ◦<br />

F<br />

C<br />

E<br />

A<br />

B<br />

Exercise 25. The perimeters of an equilateral triangle and a regular hexagon<br />

are equal. If the area of the triangle is 5 square units. Find the area of the<br />

hexagon in square units.<br />

6 Score:

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