<PRE><B>Question 617861</B>



FIRST OF ALL WE START WITH SIN A = -5/6. IN WHICH ITS ON THE FOURTH QUADRANT.

 COS A IS FOUND BY USING PYTHAGORAS THEOREM. 

THEREFORE COS A = SQRT 11 / 6


SECONDLY WE GO WITH COS B = 11/15 . IN WHICH IT IS ON THE FIRST QUADRANT. 

SIN B IS FOUND BY USING PYTHAGORAS THEOREM.

THEREFORE SIN B = SQRT 104 / 15.

WE FIND SIN( A - B ) USING THE SIN RULE.

SINA COSB - COSA SINB 

- 5/6 * 11/15 - SQRT 11/6 * SQRT 104 /15

- 11/ 18 -  SQRT 286 / 45 

-55 - 2 SQRT 286 / 90 







NOTE

SIN ( A + B) = SINA COS B + COSA SINB 
COS (A + B) = COS A COS B + SIN A SINB 
COS (A -B) = COS A COS B - SINA SIN B
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