Friday

October 24, 2014

October 24, 2014

Posted by **Jonathan** on Thursday, April 17, 2008 at 1:45pm.

thanks ... :)

- Maths -
**bobpursley**, Thursday, April 17, 2008 at 1:51pmThe first pairing says that sinA is -4/5

If cosB is 12/13, then sinB is 7/13

Sin(A-B)=CosASinB-SinACosB, right?

- Maths -
**Jonathan**, Thursday, April 17, 2008 at 1:52pmyeah thats right, can u go on?

- Maths -
**bobpursley**, Thursday, April 17, 2008 at 1:55pmI could, but I wont. However, I will be happy to critique your work or thinking

- Maths -
**bobpursley**, Thursday, April 17, 2008 at 1:58pmError: sinA=-3/5

in all cases, sin^2 Theta + cos^2 Theta=1

- Maths -
**Jonathan**, Thursday, April 17, 2008 at 1:58pmwell, i got:

(-4/5)(12/13) - (4/5)(7/13)

therefore

(-48/65) - (28/65)

therefore:

answer = (-76/65)

- Maths -
**Reiny**, Thursday, April 17, 2008 at 1:59pmfrom if cosA = 4/5; sin <0 we know that A is in the fourth quadrant and sinA = -3/5

from cosB = 12/13; 0<B<90 we know sinB = 5/13

sin(A-B) = sinAcosB - cosAsinB

= (-3/5)(12/13) - (4/5)(5/13)

= -56/65

- Maths -
**bobpursley**, Thursday, April 17, 2008 at 1:59pmchange the Sin A in the first term, and it works.

- Maths -
**Jonathan**, Thursday, April 17, 2008 at 1:59pmi knew that was wrong, coz my answer should be in the 50's haha..thanks though, great help

can i ask how you got sinA and sinB with that information :)

no point in me just copying it i would like to know how you got it

- Maths -
**bobpursley**, Thursday, April 17, 2008 at 2:02pmIn any angle, the sum of the squares of the cosines and sines is equal to one. Use that to solve.

**Answer this Question**

**Related Questions**

math - find all solutions in the interval [0,2 pi) sin(x+(3.14/3) + sin(x- 3.14/...

Trigonometry - I need to prove that the following is true. Thanks. csc^2(A/2)=...

further mathematics - Let P=(cosA sinA) (sinA cosA) Q=(cosB sinA) (sinB cosA) ...

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

MathsSs triG - Consider sin(x-360)sin(90-x)tan(-x)/cos(90+x) 1.A.SIMPLIFY sin(x-...

trig - How to do this one? (sina/1-cosa) + (1-cosa/sina) = Also, wanted to ask ...

math (trig) - i have some problems doing trig the first one is: Show that cos(x/...

tigonometry - expres the following as sums and differences of sines or cosines ...

Precal - I do not understand how to do this problem ((sin^3 A + cos^3 A)/(sin A...

math - Eliminate the parameter (What does that mean?) and write a rectangular ...