Can you tell me when to use the formula r2= a2+b2 + 2ab cos theta. I mean I have seen this formula where instead of -ab cos theta it uses +2ab cos theta. Thanks
@@EngineeringCorner , I have been accustomed to using the same formula with yours, but I have come across the other formula in a book and in some video presentation that make me wonder whether it is a separate formula to use in a special case or a typo error. However, judging from the textbook presentation, it seemed a derivation of formula. : R2 = a2+b2 + 2ab cos (180 - theta) Leading to: R2 = a2+b2 - 2ab cos theta. Not, sure if the first formula is tobe used it if the angle given in the problem is to be subtracted to 180, and use the second formula, if subtraction of angles will not be done.
This is an EXCELLENT Video, thank you for the explaination!
great video. this is basic geometry and trig. any teacher that cares about teaching should always review for students.
just thank you, thank you , i study ENGINEERING MECHANICS IDK why my major is Chemical Engineering
Very good video really helped me understand the method!
May God bless you brother
Can you tell me when to use the formula r2= a2+b2 + 2ab cos theta. I mean I have seen this formula where instead of -ab cos theta it uses +2ab cos theta. Thanks
Besides the occasional typo, I have not seen a "+2abcos(theta)" used. Law of cosines formula contains the minus sign.
@@EngineeringCorner , I have been accustomed to using the same formula with yours, but I have come across the other formula in a book and in some video presentation that make me wonder whether it is a separate formula to use in a special case or a typo error. However, judging from the textbook presentation, it seemed a derivation of formula. :
R2 = a2+b2 + 2ab cos (180 - theta)
Leading to:
R2 = a2+b2 - 2ab cos theta.
Not, sure if the first formula is tobe used it if the angle given in the problem is to be subtracted to 180, and use the second formula, if subtraction of angles will not be done.
thanks men
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agree