Post Go back to editing

KCC's Quizzes AQQ290 about a triangle coming from the Hell

So, after a long (and deserved) summer vacation, we can suppose your brain is now fully energized and ready to tackle complex problem! 

OK, I know the 2 famous laws about vacations!

1. Vacations are always too short (even if you had 4 weeks)!

2. They always occur in wrong moments (i.e. you were disturbed by any kind of urgencies).

1. First, the quote of the week: "People often say that motivation doesn't last. Well, neither does bathing - that's why we recommend it daily" - Zig Ziglar

                                                        

                                             Source: encrypted-tbn0.gstatic.com/images

2. New challenge: it's a geometry problem, about a triangle that comes from hell... Be careful, there is a trap...

                       

A right triangle has a hypothenuse of 10 cm and an altitude to the hypothenuse of 6 cm.

Question: What is the area of the triangle ABC?

Good luck! And try to be among the first ones!

Also, don't hesitate to share such quizzes with colleagues or friends!

Please share your answer to view other submitted answers
Parents
  • The triangle cannot exist as a hypothenuse of 10cm is not compatible with an altitude of 6cm. In fact, say x= cathetus 1, y= cathetus 2, t= hypothenuse, h= altitude to the hypothenuse, A= area of triangle ABC. Then you have A=x*y/2 and A=t*h/2. Also, from Pythagoras you have: x^2 + y^2 = t^2. By using this data, you end up in the equation: x^4 - t^2 * x^2 + (t*h)^2 =0. Replace z=x^2 and then you have: z^2 - t^2 * z + (t*h)^2 = 0. Now, this equation doesn't have any real solution, its discriminant being Δ=sqrt (t^4 - 4* t^2 * h^2) < 0. Since t=10cm, you can see that the maximum value of h for the existence of the triangle is any value lower than 5cm.  

Reply
  • The triangle cannot exist as a hypothenuse of 10cm is not compatible with an altitude of 6cm. In fact, say x= cathetus 1, y= cathetus 2, t= hypothenuse, h= altitude to the hypothenuse, A= area of triangle ABC. Then you have A=x*y/2 and A=t*h/2. Also, from Pythagoras you have: x^2 + y^2 = t^2. By using this data, you end up in the equation: x^4 - t^2 * x^2 + (t*h)^2 =0. Replace z=x^2 and then you have: z^2 - t^2 * z + (t*h)^2 = 0. Now, this equation doesn't have any real solution, its discriminant being Δ=sqrt (t^4 - 4* t^2 * h^2) < 0. Since t=10cm, you can see that the maximum value of h for the existence of the triangle is any value lower than 5cm.  

Children