Geometry problems 9 (80..89) problems 70..79 80. In picture below AB=AC=AD Calculate angle x. 81. In picture below three equal circles are laying tight in perpendicular triangle ABC. Calculate radius r of the circles. 82. In a square circles with radius R and r lay tight between quarter circles. Center of quarter circles lay on vertex of square. Calculate the ratio R/r. 83. Prove that the area of triangle ABC is [ABC] = pq 84. Calculate angle x. 85. Two lines separate square ABCD in three equal parts. The distance of the lines is 1. Calculate the area of the square. 86. Below is pictured a regular hexagon and a random point inside. Calculate area x. 87. Calculate the shaded area A. 88. Calculate the shaded area. 89. Calculate the ratio of green/orange square areas.