84 + 45 = 3(28 + 15)

No
Yes

The trigonometric ratios sine and secant are reciprocals of each other

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?

Which best explains why this triangle is or is not a right triangle ?