Conics: equation of chord proof (need help please) (1 Viewer)

[IAU001]

this is in the cambridge 4 unit textbook on pg 89 under the subheading 'ellipse'. i dont understand how they got from LHS to middle, and then from middle to RHS. im really weak in trig and dont understand how they did anything in this step.

 

[Affinity]

LHS to middle.. it's a trig identity.. look up something along the lines of sums to products

Mid to RHS.. hmm you should be able to see this.

 

[IAU001]

LHS to middle.. it's a trig identity.. look up something along the lines of sums to products

Mid to RHS.. hmm you should be able to see this.

oohhhh these ones:

thanks affinity. but nope i still dont see whats going on from middle to RHS suck at trig.

 

[Arowana21]

u need to know a couple more trig identities, i think they should be in the 3U Fitzpatrick book

 

[lolman12567]

Middle to RHS isnt trig, its just 2sin and -2sin cancelling. leaving a minus which goes infront of b/a.

 

[IAU001]

wtf. im retarded. thanks guys!

 

[Arowana21]

wtf ur on about

 

[Timothy.Siu]

lol, this stuff isn't in the 3U syllabus anymore

 

[clintmyster]

lol, this stuff isn't in the 3U syllabus anymore

but its used in 4u yeah?

 

[Timothy.Siu]

but its used in 4u yeah?

lol i'm not sure actually. but i know it anyway

 

[Arowana21]

it isnt taught in 3U, that is a definite, BUT it is still in the syllabus. ALL u need to do is use point gradient formula to find the equation of the chord, but halfway through ur working u will get

(something - something)/(something + something) {i cant really remember wat it was but i can remember it was in this form.
Then u should apply ur trig identities.

this is only 4U