2015 · Q39
If (x+40)^{}(x+20)^{}(3x)^{}(70-x)^{}(50-x)^{}=1 then the value of x is equal to
Elementary MathematicsStatistics
- A30
- B20
- C15
- D10
Explanation
tan(70 - x) = cot(x + 20) and tan(50 - x) = cot(x + 40), so the product collapses to tan(3x) = 1, giving 3x = 45 deg and x = 15. Hence option (c).