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secondary 3 | A Maths
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Hi, could you kindly advise me the working solution for this question please? Thanks!!!
Date Posted: 3 years ago
Views: 369
2/(cotA tan2A)
= 2 / (1/tanA x 2tanA/(1 - tan²A) )
= 2 / (2 / (1 - tan²A) )
= 2 x (1 - tan²A)/2
= 1 - tan²A
= 2 / (1/tanA x 2tanA/(1 - tan²A) )
= 2 / (2 / (1 - tan²A) )
= 2 x (1 - tan²A)/2
= 1 - tan²A
Some of my students only learnt the double angle formula in their schools in Sec 4, including my two tuition centre students (one of them I personally taught in Sec 3).
And even amongst those who have learnt them, they still continue to write
sin (A + B) = sin A + sin B
cos (A - B) = cos A - cos B
as though it is algebraic expansion of brackets. The same students have also done things like
ln (a + b) = ln a + ln b
treating ln a as ln times a.
And even amongst those who have learnt them, they still continue to write
sin (A + B) = sin A + sin B
cos (A - B) = cos A - cos B
as though it is algebraic expansion of brackets. The same students have also done things like
ln (a + b) = ln a + ln b
treating ln a as ln times a.
They're too used to multiplying out brackets
Good evening Mr J and noted with thanks :)
Welcome
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Good evening Candice! Here are my workings for this question. Have you learnt the addition angle formulae and the double angle formulae for trigo?
Date Posted:
3 years ago
Good evening Mr Eric and thank you so much. I understand your working solution :)
And yes, I've learnt both formulae for trigo.
I am struggling on another question right now. I will be posting up for help in a minute, I am not sure if you have time to help me with a 2nd question...I certainly hope you do :)
And yes, I've learnt both formulae for trigo.
I am struggling on another question right now. I will be posting up for help in a minute, I am not sure if you have time to help me with a 2nd question...I certainly hope you do :)
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