Given sin A 35 A Q4 and cos B squareroot 215 B Q3 Find sin

Given sin A = -3/5, A Q4 and cos B = -squareroot 21/5, B Q3. Find sin(A - B)

sinA=-3/5

In quadrant 4 cos theta is positive

opposite=3 hypotenuse=5

adjacent =sqrt(5²-3²)=4

cos A= 4/5

cos B=-sqrt21/5

In third quadrant sin theta is negative

adjacent=sqrt 21

hypotenuse=5

Therefore opposite=sqrt(5²-sqrt21²)=2

sin B=-2/5

sin(A-B)=sinA cos B-cos A sin B

= (-3/5)(-sqrt21/5)-(4/5)(-2/5)= (3sqrt21/25)+ (8/25)= (3sqrt21 + 8)/25