trigonometry

• sin (a+b) = sinA cosB + cosA sinB
• sin(a-b) = sinA cosB - cosA sinB
• cos (a-b) = cosA cosB + sinA sinB
• cos (a+b) = cosA cosB - sinA sinB
• tan (a+b) = (tanA + tanB)/(1 - tanA tanB)
• tan (a-b) = (tanA - tanB)/(1 + tanA tanB)
• sin = opp/hyp
• tan = opp/adj
• csc = hyp/opp
• sec = hyp/adj
• cot = adj/opp
• Q1 = s+, c+, t+
• Q2 = s+, c-, t-
• Q3 = s-, c-, t+
• Q4 = s-, c+, t-