In △PQR, what is the length of QR
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Question

In △PQR, what is the length of QR
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anonymous · Answer

$$21\sqrt{2}$$
$$42\sqrt{2}$$
$$42\sqrt{3}$$

21

anonymous · Answer

What are the directions of the problem. Are you allowed to use trig functions?

anonymous · Answer

Because trig is the easiest way.

anonymous · Answer

$$\sin 45=\frac{QR}{42}$$

anonymous · Answer

im sure i can if u get one of them answers

king · Answer

plus or minus 21

king · Answer

use Pythagoras theorem

anonymous · Answer

It can't be minus if we are talking about a lenght @King

anonymous · Answer

There are rules for a 45, 45, 90 triangle. Just like with a 30,60,90 http://zonalandeducation.com/mmts/miscellaneousMath/tri454590306090/tri454590306090.htm So, 42/2*sqrt(2)

king · Answer

oh yeah sry 21

king · Answer

use Pythagoras theorem

mertsj · Answer

That is one of the special right triangles.  The 45-45-90.  In such a triangle you multiply a leg by sqrt2 to find the hypotenuse.  Correspondingly, you divide they hypotenuse by sqrt2 to find the leg.  You are trying to find the leg.

mertsj · Answer

$$\frac{42}{\sqrt{2}}=\frac{42\sqrt{2}}{2}=21\sqrt{2}$$

anonymous · Answer

ohh okay but someone else said it was the 42/2 so which one idk i dont have a teacher really im homeschooled

anonymous · Answer

$$21\sqrt{2}$$Is the right answer mak_12

anonymous · Answer

Maybe macnaljj made a typo.

anonymous · Answer

42/2 is 21. I was pointing out that h/2*sqrt(2) is the rule for the other sides. Could have done better.

anonymous · Answer

can someone help me with the question i just posted n then tell me how 
and its okay no promblem there @mcnalljj