C3 Identities question

Well, I guess it be be re-written as tan(45+7.5)

7.5 is half of 15 which is half of 30

then use addition formulae i guess?

EDIT: it says hence so it wants you to use the thing that you proved in a)

Reply 2

Original post by creativebuzz

I can do part a but I was wondering if there's a method I can use to approach part b because I could be here forever thinking of a value of x and y that give me 52.5 and give me the exact values I need..

y=52.5-x

and also

105=60+45

(edited 8 years ago)

Reply 3

creativebuzz

OP

Original post by Dancatpro

Well, I guess it be be re-written as tan(45+7.5)

7.5 is half of 15 which is half of 30

then use addition formulae i guess?

EDIT: it says hence so it wants you to use the thing that you proved in a)

Yeah I understand the whole hence part, but what made you pick 45 and 7.5 and not any other numbers which make 52.5?

Reply 4

creativebuzz

OP

Original post by Renzhi10122

y=52.5-x

and also

105=60+45

Can you elaborate that abit? I'm not quite sure what you're doing...

Reply 5

Dancatpro

Original post by creativebuzz

Yeah I understand the whole hence part, but what made you pick 45 and 7.5 and not any other numbers which make 52.5?

Because you can make those numbers easily using special triangles

Reply 6

Original post by creativebuzz

Can you elaborate that abit? I'm not quite sure what you're doing...

Use part a and set

y=52.5-x

and then you'll have to use your addition formulae to find cos105 and sin105 and expand.

Reply 7

creativebuzz

OP

Original post by Dancatpro

Because you can make those numbers easily using special triangles

So you're trying to say that the method behind it is to opt for the numbers made in special triangles?

Reply 8

Dancatpro

Original post by creativebuzz

So you're trying to say that the method behind it is to opt for the numbers made in special triangles?

I might be completely wrong :/

Reply 9

broconomist

Original post by Dancatpro

I might be completely wrong :/

x = 22.5
y = 30

then solve using 2x=45 and 2y=60

(edited 8 years ago)

Reply 10

Original post by broconomist

x = 7.5
y = 45

then solve using 2x=30 and 2y=90

Btw, 7.5*2=15

Reply 11

Personally, i think the easiest way to do is to just let x=0

Reply 12

broconomist