Question 41·200 Super-Hard SAT Math Questions·Geometry and Trigonometry
Triangle is inscribed in a circle with radius 65. The length of is 130, and the length of is 126. Which choice equals ?
When a triangle is inscribed in a circle and the radius is given, immediately check whether any side equals the diameter . If it does, that side is a diameter and the angle opposite it is , turning the problem into a right-triangle question. Then use the Pythagorean theorem to find the missing side and simplify the requested ratio carefully.
Hints
Look for a diameter
Use the radius to find the diameter of the circle, and compare it to the side lengths of the triangle.
Use the inscribed right angle fact
If one side of an inscribed triangle is a diameter, what can you conclude about the angle opposite that side?
Finish with a right-triangle relationship
Once you know which angle is , apply the Pythagorean theorem to find the missing side, then form and simplify.
Desmos Guide
Compute the missing leg
Enter the expression sqrt(130^2-126^2) to compute .
Form the ratio
Enter (sqrt(130^2-126^2))/126 to compute as a decimal.
Match to an answer choice
Compute each option as a decimal (for example, enter 16/63, 16/65, etc.) and choose the one that matches the decimal value of .
Step-by-step Explanation
Identify the right angle
The circle has radius 65, so its diameter is .
Since , is a diameter of the circle. An angle that subtends a diameter is a right angle, so .
Use the Pythagorean theorem to find
In right triangle , is the hypotenuse and and are legs. So:
Substitute and :
So .
Compute the requested ratio
So the correct choice is .