You are not logged in.
Pages: 1
Hi mathsyperson, thank you for your reply.
Does that mean everytime if I use cross products to find angle I must always apply 180-x otherwise the answer will be wrong in term of degree?
If so, it seems like dot products is more precise in this.
Is there any significant advantage over dot products when using cross products to find angle?
Is there any instance where one can only use cross products to find angle of two vectors?
Hi,
When I use cross products to find an angle of 2 vectors as compared to using dot products, I realised that it's wrong.
Using dot products to find angle
===================================
V = (-3, 1, 0)
W = (1,2,0)
Formula: cosΘ = V dot W /( |V||W| )
=> cosΘ = -1 / √50
=> cosΘ = -0.141421
Inverse of cos gives 98.13° which is the correct angle.
Using cross products to find angle
===================================
V = (-3, 1, 0)
W = (1,2,0)
Formula: |VxW| = |V||W|sinΘ
=> sinΘ = |VxW| / |V||W|
=> sinΘ = 7 / √50
=> sinΘ = 0.989949
Inverse of sin gives 81.869898° which is a wrong angle.
But if 180°-81.869898° gives the right answer.
Why is that so? Is it something wrong with the formula?
Please advice, thank you so much for your time.
Pages: 1