Sine Or Cosine Rule? | Trigonometry | Maths | FuseSchool

Not every triangle is a right-angle triangle, so we can't always use Pythagoras and SOHCAHTOA to find missing sides and missing angles. We instead use the sine rule or the cosine rule. They can both be used to find either missing sides or missing angles in any triangle (right angle or not). We label the sides as a, b and c, and angles as A, B and C.

We need to work out whether to use the sine rule or the cosine rule.

The sine rule is easier, so look for that one first. The sine rule is based on opposite pairs: you need an angle and the side opposite it, then you need either an angle and you want the opposite side OR you need a side and you want the opposite angle.

If we don't have the right combination of sides and angles for the sine rule, then we can use the cosine rule. For the cosine rule, we either want all three sides and to be looking for an angle, OR we need to have a side, angle and side all next to each other, and to then be wanting to find the third side.

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[saishrinithi]

This was exactly what I was looking for. It's crazy how they could explain in 2 minutes but my teachers couldn't explain it in 2 weeks.

[aleenaasif]

are the videos from 2006 really helping? excuse me this is from 2017 and yes, it IS helping

[stefaniamueller]

I should start sending these videos to my teacher cause this 2 min video made more sense than a month of her teaching did.

[renan]

Thank you. Great explanation. I won't forget it anymore !

[借一盏月色]

Where is the cosine rule video, i really need it ! Thanks

[cengiz]

thank you! very helpful video, exactly what i needed

[HateHater]

Can you raised the presenters voice to match the volume of your intro? I have to adjust each time cause I have to keep it quiet but then I can’t hear

[ibrarmohammed]

The music in the background is too loud. Its difficult to hear you. Why have the music and if so, why hav so loud

[evanjackson]

Nice and concise but still giving all the detail. Cheers

[sulemansaleem]

ive just realised how much time and money ive wasted going to school *sad emoji
also do keep making more vids, its really helpful :)

[brycepetruszewski]

very helpful but there's no cosine rule video

[sudoman]

Why is the music louder than her voice smh. Why is there even music?

[simangalisompofu]

can you find length of one side of a triangle using 3 angles and one side

[imadj]

Thanks for this Video, Very helpful 😊😊😊

[geatsuneee]

Yep. Watching this video for 10th Grade Trigonometry class.

[rahulk]

Who's the lady explaining this video?

[xaviferrandizward]

If people worked out the missing angles of the triangles. What u get?