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Mathematics: Post your doubts here!

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Prove the identity (sin x + cos x)(1 − sin x cos x) ≡ sin3 x + cos3 x. [3]
(ii) Solve the equation (sin x + cos x)(1 − sin x cos x) = 9 sin3 x for 0◦ ≤ x ≤ 360◦. can anyone solve part (ii) i dont get it @A

Take sin3x + cos3x as (sinx + cosx)(1 - sinx cosx)
So you get...
sin3x + cos3x = 9sin3x

Divide both sides by sin3x

1 + cos3x/sin3x = 9
1 + tan3x = 9
tan 3x = 8
3x = tan^-1(8)
x= 27.6 <=== Is this correct?
 
Messages
887
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466
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73
Take sin3x + cos3x as (sinx + cosx)(1 - sinx cosx)
So you get...
sin3x + cos3x = 9sin3x

Divide both sides by sin3x

1 + cos3x/sin3x = 9
1 + tan3x = 9
tan 3x = 8
3x = tan^-1(8)
x= 27.6 <=== Is this correct?
answer is 26.6
 
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2,703
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273
Prove the identity (sin x + cos x)(1 − sin x cos x) ≡ sin3 x + cos3 x. [3]
(ii) Solve the equation (sin x + cos x)(1 − sin x cos x) = 9 sin3 x for 0◦ ≤ x ≤ 360◦. can anyone solve part (ii) i dont get it @A
is it p1?
 
Messages
887
Reaction score
466
Points
73
Take sin3x + cos3x as (sinx + cosx)(1 - sinx cosx)
So you get...
sin3x + cos3x = 9sin3x

Divide both sides by sin3x

1 + cos3x/sin3x = 9
1 + tan3x = 9
tan 3x = 8
3x = tan^-1(8)
x= 27.6 <=== Is this correct?
lol chutia me i have solved this on my own now thanks anyways
 
Messages
2,703
Reaction score
3,939
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273
Guys . tommorow we al have P1 . So i was thiinking why dont we share some tips that hepl us in solving papers . Let me the first to initiate :
  1. colinear of parallell vectors have a ratio of k . EG if a and b are colinear then a^/b^ =k .

what?
 
Messages
192
Reaction score
103
Points
53
Guys . tommorow we al have P1 . So i was thiinking why dont we share some tips that hepl us in solving papers . Let me the first to initiate :
  1. colinear of parallell vectors have a ratio of k . EG if a and b are colinear then a^/b^ =k .

I didn't get it.
 
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haha . Look if two vectors are collinear of parallel then they have a common ratio between them . suppose a=(2.4.6) and b=(1.2.3)

a/b =2 and so they are both collinear
 
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192
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53
haha . Look if two vectors are collinear of parallel then they have a common ratio between them . suppose a=(2.4.6) and b=(1.2.3)

a/b =2 and so they are both collinear

OR... Their unit vectors are equal.
 
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