Trigonometric Identities & Equations 11 • Solving Simple Equations • P1 Ex10D • 🚀

Edexcel Pure Year 1

Weds 17/6/20

[chuchu]

There is a good way on how to solve trig identities, I learnt it from UpLearn

When the equation is equal to zero, you can use tan identity, eg.

aSinø = bCosø
aSinø + bCosø = 0
aSinø - bCosø = 0

You can't use the tan identity when the equation isn't equal to 0, eg.

aSinø = bCosø + c
aSinø + bCosø = c

For these you should use the Pythagorean identity

[shepherddown]

Dear sir, 9.54 min, for -30 adding 360 degree can get 330 which is in the range of 0<theta<360, pls correct me if I was wrong

[jamie]

Hello sir, thanks for producing these amazing videos, I had a quick question and that is if I can just stick to your method of solving trig equations rather than using other methods such as the quadrant rule and the graph method, can I still be awarded marks in the exam as I am still applying the trig laws used by you, and I just find this method much easier to use and apply rather than the other methods, which I find difficult to use.

[zain]

Hi for question 2 at 9:33 should it be 210, 330 degrees not -30 as the domain is 0 to 360?

[mayoul]

Hello sir i remember you said that with tanx we only add on 180, but not -180 and so i was wondering why did you minus 180 from tanx .many thanks

[fixiecats]

Is it okay to be watching Edexcel videos whilst taking AQA examboard qualifications? There are no other AQA videos as good as this!

[elixir]

at 10:01. how can you do -30 + 360 = 330, when you said to do 180 - x ? thanks for the help sir it is greatly appreciated

[LutoBam]

I missed the lesson for CAST diagrams and I don’t like that method anyway, i much prefer yours

[Gottaluvsb]

what about if we had a minus ? e.g costheta = -cos40 ? how do we solve this please