Use sine rule you find the length of the line which is facing angle 30°. Consider the triangle having the red line, L and use cosine rule to find the length, L of the red line.
From the second figure, label center O of the quarter circle and join the apex of the red line to the center, O. Since, the base angle of the triangle formed are equals (Isosceles triangle), let each angle be α (alpha) then, the apex angle of this triangle is 180° - 2α. Use cosine rule to find an important angle to help you solve second step by considering triangle formed by red line 4 units of the yelllow rectangle. Resolve the relationship between the 4 units length of this triangle and the important angle obtained to find the required area of the yellow region.
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1 окт 2024
