Find the angle between the given vectors to the nearest tenth of a degree. u = , v =

Question

Find the angle between the given vectors to the nearest tenth of a degree. u = <8, 4>, v = <9, -9>

waleed_imtiaz · Answer

u know the formula to calculate the angle ???

anonymous · Answer

no...

anonymous · Answer

do you?

waleed_imtiaz · Answer

the formula is : cos(theta) = u.v/|u| |v|
In the numerator its the dot product of u and v and in the denominator its the magnitude of u and v seperately...and then take cos inverse to find theta...

anonymous · Answer

okay so numerator = 36?

anonymous · Answer

denominator = 12.92

waleed_imtiaz · Answer

numerator is right.

waleed_imtiaz · Answer

8.99*12.72 multiply these two u will get the denominator ..got it?

anonymous · Answer

im confused with the denominator

anonymous · Answer

oh okay so the denominator is 114.3528

waleed_imtiaz · Answer

okey then first calculate magnitude of u ... 
|u|= $$\sqrt{8^{2}+4^{2}}$$ u will get 8.99

waleed_imtiaz · Answer

yes now u are rite

anonymous · Answer

so the angle is 71.65?

anonymous · Answer

can you help me with a few more?

waleed_imtiaz · Answer

I can try...

anonymous · Answer

Find the fourth roots of 256(cos 240° + i sin 240°).

waleed_imtiaz · Answer

first simplify the expression ..and then do like this....if i have to find the fourth root of unity then I will do x^4=1
x^4-1=0
simplify it and u will get x=1,-1, iota, -iota.... in the same way first write the value of cos 240 and sin 240 and make it simple to operate and then do like above as I told

anonymous · Answer

I don't understand that at all.. lol