Mathematics: Post your doubts here!

[vaishster]

Cos (5α+θ)=sin(θ-3α). find the least positive value for α ???????????? how pls also explain how to do it

 

[IgoforA]

need help for 1. b) ??

 

[zenyatales]

@ IgoforA

i got this.

hope this helps . also, the answer is explained in the ER of that year.

 

[Xthegreat]

[Oct/Nov P31 2011]
With respect to the origin O, the points A and B have position vectors given by

OA = i + 2j + 2k and
OB = 3i + 4j. The point P lies on the line AB and OP is perpendicular to AB.

(i) Find a vector equation for the line AB. [1]
(ii) Find the position vector of P.

how do u find the position vector? i dont get the answer.

 

[Xthegreat]

Cos (5α+θ)=sin(θ-3α). find the least positive value for α ???????????? how pls also explain how to do it

thats it? the full question is that short?

 

[vaishster]

yes .. its a question frm a book... do u kno how 2 solve it??

 

[shressubha]

There are 3 values of x , (one of which is 158.9 ) in the interval 0◦ ≤ x ≤ 180◦ which satisfy the equation sin 3x +2cos3x = 0. How to find the other two values of x???

 

[mrpaudel]

I got the answer a=-3pi/16.......i think this is correct..this is how u do it..

Cos(5a+θ)=Sin(θ-3a)
or,Cos(5a+θ)= -Cos(3pi/2 -θ+3a) [ since, Cos(270-angle)=-Sin(angle) ]
Cos is cancelled...so..
or,5a+θ= -3pi/2 +θ -3a
solving this..we get a=-3pi/16

 

[mrpaudel]

There are 3 values of x , (one of which is 158.9 ) in the interval 0◦ ≤ x ≤ 180◦ which satisfy the equation sin 3x +2cos3x = 0. How to find the other two values of x???

do this way..... Sin3x=-2Cos3x
squaring both sides...Sin^2 (3x)=4Cos^2 (3x)
add Cos^2 (3x) on both sides..

1=5Cos^2 (3x)...now hope..u can solve it and get answers like...38.** , 98.** and....as u stated..!!

 

[vaishster]

fyi the answer is 11.25 degrees. if anyone gets tat ans pls post how to do it

 

[vaishster]

SRYYYYYYYYY I MADE A BIG MISTAKE question ws sin(5α+θ)=cos(θ-3α)

 

[ambitious1]

May/June 2011 - 12 - Q6(i)

Can someone please show me the exact way to simplify it out??

 

[rz123]

f(x) = x+3 / 2x+1
f f (x) = x

f( x+3) / 2x-1

x+3 / 2x +1 + 3 divided by 2 ( x+3) / 2x-1 -1

x+3+6x-3 / 2x-1 divided by 2x+6 /2x-1 -1

x+ 6x / 2x-1 multiply by 2x-1/ 7 now we will simplify after we have took the reciprocal so it will end up being only x.

 

[mrpaudel]

SRYYYYYYYYY I MADE A BIG MISTAKE question ws sin(5α+θ)=cos(θ-3α)

well if this is the question..answer is 11.25..do this way..
Sin(5a+θ)=Cos(θ-3a)
or, Sin(5a+θ)=Sin{90+(θ-3a)} [ since, sin(90+B)=CosB ]
Sine cancelled...
or, 5a+θ=90+θ-3a
or,8a=90
or,a=90/8 =11.25

 

[mrpaudel]

May/June 2011 - 12 - Q6(i)

Can someone please show me the exact way to simplify it out??

u dont have a book endorsed by CIE???? Pure maths 2 & 3....there is a formula...simply use that...!!

 

[ambitious1]

I do have it, though am only doing AS level now, so i don't really know about it.. Can u type down the formula or tell me which page is it on?

 

[vaishster]

s11 qp12.... q4 ii) ??? tangent it makes wit x axis .. how to do tat??

 

[SincerlyMe]

Need help with Q:8 , M/J/2011 (11)
Thanks in advance !

 

[1357913579]

please help me clear this oct/nov 2006 paper no.9 they asked for volume so first we have to find are of triangles and rectangles for triangle why dont we find by multiplying 5x with 5x as one is verticle the other is horizotal so 0.5 multiply by 5x multiply y 5x why not and for november05 no.5 as it gts fit in cone so isnt thst means they have same volume please helpppppppppppppppppppppppp

 

[markskoop]

Solve this problem its scuking my head!! posting.php?mode=reply&f=26&t=10916#
ASAP