Battle of Old Trafford | Math Problem

Click here to read the complete problem statement.

How can I solve it? Help me.

a=?,b=?,c=? and d=?.
Can anyone tell me?

No need to find a, b, c and d individually

Bro, You don’t need to find any values for a,b,c,d. Just read the problem properly…
a^2+b^2=1, c^2+d^2=1 and ac+bd=0…

So this is very common that ab+cd will be same as ac+bd… ZERO