Maths A Level question help

Please can someone explain this to me, I understand everything until the bit where it says "Cancel sinθ as θ≠0° or 180°". Why do you cancel sin??

THANKS!

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Original post by jarjarbinkss

Please can someone explain this to me, I understand everything until the bit where it says "Cancel sinθ as θ≠0° or 180°". Why do you cancel sin??

THANKS!

Because then you're left with a single variable of cos to solve for?

You're allowed to cancel because sin is not 0, so dividing by it is allowed.

Reply 2

jarjarbinkss

OP

13

Original post by RDKGames

Because then you're left with a single variable of cos to solve for?

You're allowed to cancel because sin is not 0, so dividing by it is allowed.

oh wait so they have just divided the whole thing by sin. Why can you not divide by sin if it equals 0 then? is it because sin 0 = 0 and dividing by 0 isn't allowed anyway?

Reply 3

-Mathematician-

11

We cancel the sin(ø) as it’s the next logical step. Instead of having ø appear three times in the equation we can eliminate two of them, making it much easier to solve.
Divide both sides by ‘sin(ø)’
This leaves you with [2cos(ø)]/5 = 1/4
Then multiply both sides by 5 giving you 2cos(ø) = 5/4
This can then be solved with ease.

Original post by jarjarbinkss

oh wait so they have just divided the whole thing by sin. Why can you not divide by sin if it equals 0 then? is it because sin 0 = 0 and dividing by 0 isn't allowed anyway?

Dividing by 0 is obviously not allowed, yes, and

\sin(180n)=0

for any multiple of 180 as the argument.

Reply 5

jarjarbinkss

OP

13

Original post by RDKGames

Dividing by 0 is obviously not allowed, yes, and

\sin(180n)=0

for any multiple of 180 as the argument.

yeah yeah i remember that now thanks

Reply 6

jarjarbinkss

OP

13

Original post by -Mathematician-

We cancel the sin(ø) as it’s the next logical step. Instead of having ø appear three times in the equation we can eliminate two of them, making it much easier to solve.
Divide both sides by ‘sin(ø)’
This leaves you with [2cos(ø)]/5 = 1/4
Then multiply both sides by 5 giving you 2cos(ø) = 5/4
This can then be solved with ease.

thank you very much

Maths A Level question help

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