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Lines, angles, and triangles SAT question

Math · Geometry and Trigonometry · Hard · Answer it here, explanation included.

  • Triangle upper A upper C upper D partially overlaps triangle upper E upper B upper D.
  • Point upper C is on line segment upper B upper D.
  • Point upper E is on line segment upper A upper D.
  • The measure of angle upper A upper E upper B is x°.
  • A note indicates the figure is not drawn to scale.

 

In the figure, . The measure of angle is , and the measure of angle is . What is the value of ?

Enter a number or fraction (like 3/17 or 0.176). Press Enter to check.

ExplanationShow

The correct answer is . It's given that in the figure, . Thus, triangle is an isosceles triangle and the measure of angle is equal to the measure of angle . The sum of the measures of the interior angles of a triangle is . Thus, the sum of the measures of the interior angles of triangle is . It's given that the measure of angle is . It follows that the sum of the measures of angles  and  is , or . Since the measure of angle  is equal to the measure of angle , the measure of angle  is half of , or . The sum of the measures of the interior angles of triangle is . It's given that the measure of angle is . Since the measure of angle , which is the same angle as angle , is , it follows that the measure of angle is , or . Since angle and angle form a straight line, the sum of the measures of these angles is . It's given in the figure that the measure of angle is . It follows that . Subtracting from both sides of this equation yields .

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