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secondary 3 | A Maths
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need help with addition formulae, pls explain too as i dont understand anything from this topic
Date Posted: 3 years ago
Views: 277
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Q1 a, b, c
Date Posted:
3 years ago
i will mark this question as done first as i have to post another qn
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It is important to know how the formulae work. The proof of such formulae is quite hard, so chances are you will be memorising the formula rather than understand the idea behind it.
Also note that sin and cos functions do not follow arithmetic such as
sin (A + B) = sin A + sin B
ie rainbow expansions do not apply here, but this error is very common amongst students.
Also note that sin and cos functions do not follow arithmetic such as
sin (A + B) = sin A + sin B
ie rainbow expansions do not apply here, but this error is very common amongst students.
Date Posted:
3 years ago
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Q6
I will only look at Q3, Q4 and Q5 some other time if I am free and I can remember. Also, I won't be answering questions in this forum that frequently anymore due to increased workload.
I will only look at Q3, Q4 and Q5 some other time if I am free and I can remember. Also, I won't be answering questions in this forum that frequently anymore due to increased workload.
Date Posted:
3 years ago
do sin cos tan 180 and 360 equates to either 1 or 0? if so, does that mean for these type of questions when we cant add or subtract the special angles to get the number we want to obtain then we will just use 180 or 360?
at part (i), how did 2 + 3/ sqrt 3 become 2 + sqrt 3
btw when sec^2 x become 1 + tan^2 x, why isnt the 255 times by 1 which makes it 255 + 255 tan^2 x
"do sin cos tan 180 and 360 equates to either 1 or 0? if so, does that mean for these type of questions when we cant add or subtract the special angles to get the number we want to obtain then we will just use 180 or 360?"
These are some further special angles to know
sin 0 = 0
sin 90 = 1
sin 180 = 0
sin 270 = -1
sin 360 = 0
cos 0 = 1
cos 90 = 0
cos 180 = -1
cos 270 = 0
cos 360 = 1
tan 0 = 0
tan 90 = undefined
tan 180 = 0
tan 270 = undefined
tan 360 = 0
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"at part (i), how did 2 + 3/ sqrt 3 become 2 + sqrt 3"
We need to rationalise 3 / sqrt 3 by multiplying both the numerator and the denominator by sqrt 3. Alternatively, we can write the 3 in the numerator as sqrt 3 times sqrt 3. Or, we can even use indices to see this.
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"btw when sec^2 x become 1 + tan^2 x, why isnt the 255 times by 1 which makes it 255 + 255 tan^2 x"
The 255 is an angle and is not supposed to be multiplied to the "1". The "1" is fixed regardless of the angle. You must be able to distinguish between an angle, especially in degrees, and a numerical value.
These are some further special angles to know
sin 0 = 0
sin 90 = 1
sin 180 = 0
sin 270 = -1
sin 360 = 0
cos 0 = 1
cos 90 = 0
cos 180 = -1
cos 270 = 0
cos 360 = 1
tan 0 = 0
tan 90 = undefined
tan 180 = 0
tan 270 = undefined
tan 360 = 0
--------------------------------------------------------
"at part (i), how did 2 + 3/ sqrt 3 become 2 + sqrt 3"
We need to rationalise 3 / sqrt 3 by multiplying both the numerator and the denominator by sqrt 3. Alternatively, we can write the 3 in the numerator as sqrt 3 times sqrt 3. Or, we can even use indices to see this.
--------------------------------------------------------
"btw when sec^2 x become 1 + tan^2 x, why isnt the 255 times by 1 which makes it 255 + 255 tan^2 x"
The 255 is an angle and is not supposed to be multiplied to the "1". The "1" is fixed regardless of the angle. You must be able to distinguish between an angle, especially in degrees, and a numerical value.
In other words, tan 255 is not the same as 255 x tan 1.
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Q3, Q4, Q5
Date Posted:
3 years ago
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Q1 d, e, f
The rest I do another time only if I am free and I can remember
The rest I do another time only if I am free and I can remember
Date Posted:
3 years ago
im still confused on which formula to use and how it works, especially for part e and f. by the way for qn1 why we dont need to make the answer a special angle tho
You need to recognise the formats. The questions in Q1 are just for you to familiarise yourself with the operations of the rule. The result does not have to be a special angle as we are not required to evaluate the expression.
i dont really understand part e and f, can you explain to me about it? will really appreciate it!
This I look later if I have time.
Part and parcel of excelling in this portion of trigo is to memorise the formulae and recognise the relevant formats.
Part and parcel of excelling in this portion of trigo is to memorise the formulae and recognise the relevant formats.
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You must not forget your earlier topics even as you proceed forward to new topics.
Date Posted:
3 years ago
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