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# Factorising Watch

1. How do you factorise this??

2. (Original post by rpnom)
How do you factorise this??

It doesn't factorise so you'd use the quadratic formula to work out tanx
3. (Original post by boredom07)
It doesn't factorise so you'd use the quadratic formula to work out tanx
Thank you! How do you use the formula to get tanx? Sorry, I've only ever done it to find x
4. b^2-4ac must be a perfect square for factorising to be possible and in this case b^2-4ac=17. tan x turns out to be (7-+root (17))/16
5. (Original post by rpnom)
Thank you! How do you use the formula to get tanx? Sorry, I've only ever done it to find x
Same as for x but this time it's tanx instead of x
6. (Original post by rpnom)
Thank you! How do you use the formula to get tanx? Sorry, I've only ever done it to find x
I substituted tanx with the variable y in my calculation.
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7. (Original post by boredom07)
I substituted tanx with the variable y in my calculation.
Thank you so much! I had a bit of last minute exam stress there haha
8. This is called a 'hidden quadratic' and if yoy are not used to them, substituting the variable for a single letter (as rpnom did above) is the way to go.

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