Explanation:
We have sinA = 4/5 and sinB = 7/25.
=> cosA = sqrt(1 - sin²A) = 3/5
=> cosB = sqrt(1 - sin²B) = 24/25
P.S. Cosine must be positive in Quadrant I.
sin(A - B)
= sinAcosB - cosAsinB
= (4/5)(24/25) - (3/5)(7/25)
= 75/125 = 3/5. (Shown)
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