Evaluate sin, cos, tan of A±B by expanding with the addition formulas.
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Why it works
The addition formulas come from rotating coordinates: sin(A+B) = sinA cosB + cosA sinB, cos(A+B) = cosA cosB − sinA sinB, tan(A+B) = (tanA+tanB)/(1−tanA tanB). Flipping B’s sign gives the difference versions. They let you find exact values like sin 75° = sin(45°+30°).
