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# quick trig question

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1. I am doing M2 right now, trying to find theta

I have arrived at the following

(costheta-sintheta)=12/15

I have not yet completed C3 trig, or even started it, since I am an AS level student.

Any explanation would be great.
2. square both sides, expand the bracket on the LHS, then sub in identities (e.g. cos^2theta = 1 - sin^2theta)
3. Never mind, its not.
4. (Original post by EconEast)
square both sides, expand the bracket on the LHS, then sub in identities (e.g. cos^2theta = 1 - sin^2theta)
1-2(sintheta*costheta)=144/225

where do I go from here?

As an AS level student I know 2 trig identities

cos squared + sin squared = 1
sin/cos=tan
5. 2sinxcosx = sin2x
that's a double angle formula you learn in c3

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