where represents the square root of the product in the brackets that follow it 
r 2 20 10 262 772 73 77 781 69 2 638 05 20 302 584 424 77 781 69 2 20 348 307 23 2 638 05 2 2 begin aligned r 2 big tiny frac 20 10 262 772 73 77 781 69 2 638 05 sqrt 20 302 584 424 77 781 69 2 times sqrt 20 348 307 23 2 638 05 2 big 2 end aligned r2 20 302 584 424 77 781 69 2 20 348 307 23 2 638 05 2 20 10 262 772 73 77 781 69 2 638 05 2 you now have 1 20 10 262 772 73 77 781 69 2 638 05 63 467 32 2 20 302 584 424 77 781 69 2 1 697 180 74 1 302 76 3 20 10 262 772 73 2 638 05 2 6 836 85 82 69 begin aligned 1 tiny 20 times 10 262 772 73 77 781 69 times 2 638 05 63 467 32 2 tiny sqrt 20 times 302 584 424 77 781 69 2 sqrt 1 697 180 74 1 302 76 3 tiny sqrt 20 times 10 262 772 73 2 638 05 2 sqrt 6 836 85 82 69 end aligned 1 20 10 262 772 73 77 781 69 2 638 05 63 467 322 20 302 584 424 77 781 69 2 1 697 180 74 1 302 763 20 10 262 772 73 2 638 05 2 6 836 85 82 69 now multiply steps two and three divide step one by the result and square it 63 467 32 1 302 76 82 69 2 0 347 begin aligned big frac 63 467 32 1 302 76 times 82 69 big 2 0 347 end aligned 1 302 76 82 6963 467 32 2 0 347 you can see how this can become very tedious with lots of room for error particularly if you re using more than a few weeks of trading data interpreting the coefficient of determination