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# Quick trig question Watch

1. Hey guys

Just a quick question on trigonometry.

So I know you use cosine rule when you have :
1. A triangle with 3 sides
2. A triangle with 2 sides and and angle between the two sides

Sine rule when you have :
1. A triangle with 1 side and 2 angles

I'm a little confused on what you do when you have a triangle with 2 sides and an angle which is not between them ( so opposite one of the sides). I remember for GCSE when I used BBC bitesize it states you use sine rule, however a cgp revision guide I have just says that the rules don't work when you have 2 sides and an able not between them.

Please could someone kindly clarify what you do if you have a triangle and 2 sides but the angle is not between the 2 sides.

2. You'd use the sine rule as the angle will be "opposite" one of the sides.

Unless you mean you're trying to find the angle in which case I have no idea sorry
3. (Original post by Aty100)
Hey guys

Just a quick question on trigonometry.

So I know you use cosine rule when you have :
1. A triangle with 3 sides
2. A triangle with 2 sides and and angle between the two sides

Sine rule when you have :
1. A triangle with 1 side and 2 angles

I'm a little confused on what you do when you have a triangle with 2 sides and an angle which is not between them ( so opposite one of the sides). I remember for GCSE when I used BBC bitesize it states you use sine rule, however a cgp revision guide I have just says that the rules don't work when you have 2 sides and an able not between them.

Please could someone kindly clarify what you do if you have a triangle and 2 sides but the angle is not between the 2 sides.

https://a44694f152ee562e38a9454969d2...%20Edexcel.pdf
look at question 4 if you mean 2 sides and not the included angle( where included angle is the angle between 2 sides)
then yes you use sine rule
4. (Original post by thefatone)
https://a44694f152ee562e38a9454969d2...%20Edexcel.pdf
look at question 4 if you mean 2 sides and not the included angle( where included angle is the angle between 2 sides)
then yes you use sine rule
Thank youu

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