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Right triangles and trigonometry SAT question

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

The side lengths of right triangle are given. Triangle is similar to triangle , where corresponds to and corresponds to . What is the value of ?

ExplanationShow

Choice B is correct. It's given that right triangle is similar to triangle , where corresponds to and corresponds to . It's given that the side lengths of the right triangle are , , and . Corresponding angles in similar triangles are equal. It follows that the measure of angle is equal to the measure of angle . The hypotenuse of a right triangle is the longest side. It follows that the hypotenuse of triangle  is side . The hypotenuse of a right triangle is the side opposite the right angle. Therefore, angle is a right angle. The adjacent side of an acute angle in a right triangle is the side closest to the angle that is not the hypotenuse. It follows that the adjacent side of angle is side . The opposite side of an acute angle in a right triangle is the side across from the acute angle. It follows that the opposite side of angle is side . The tangent of an acute angle in a right triangle is the ratio of the length of the opposite side to the length of the adjacent side. Therefore, . Substituting for and for in this equation yields , or . The tangents of two acute angles with equal measures are equal. Since the measure of angle is equal to the measure of angle , it follows that . Substituting for  in this equation yields . Therefore, the value of is .

Choice A is incorrect. This is the value of .

Choice C is incorrect. This is the value of .

Choice D is incorrect. This is the value of .

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