tan⁻1(1/4)+ tan⁻1(2/9) is equal toa)(1/2)cos⁻1(3/5)b...
Solution:
We know that tan(A+B) = (tanA + tanB) / (1-tanA tanB)
Using the above formula, we can write:
tan(1/4 + 2/9) = (tan1/4 + tan2/9) / (1-tan1/4 tan2/9)
Let's find the values of tan(1/4) and tan(2/9) using the formula:
tan(2x) = 2tanx / (1-tan^2x)
tan(1/2) = 2tan(1/4) / (1-tan^2(1/4))
Solving the above equation, we get:
tan(1/4) = (2-sqrt(2)) / (2+sqrt(2))
Similarly, we can find the value of tan(2/9) as:
tan(2/9) = (2-tan(1/4)) / (1+2tan(1/4))
Substituting the values of tan(1/4) and tan(2/9) in the above equation, we get:
tan(1/4 + 2/9) = (tan1/4 + tan2/9) / (1-tan1/4 tan2/9)
tan(17/36) = [(2-sqrt(2))/(2+sqrt(2))] + [(2-(2-sqrt(2))/(2+sqrt(2)))] / [1-((2-sqrt(2))/(2+sqrt(2)))((2-(2-sqrt(2))/(2+sqrt(2))))]
Simplifying the above equation, we get:
tan(17/36) = 1/2
Using the formula, tan2x = 2tanx / (1-tan^2x), we can find the value of tan(1/2) as:
tan(1/2) = 2tan(1/4) / (1-tan^2(1/4))
Substituting the value of tan(1/4), we get:
tan(1/2) = [2((2-sqrt(2))/(2+sqrt(2)))] / [1-((2-sqrt(2))/(2+sqrt(2)))^2]
Simplifying the above equation, we get:
tan(1/2) = 1/2
Hence, the given expression tan(1/4) * tan(2/9) is equal to:
tan(1/4) * tan(2/9) = tan(1/4 + 2/9) - tan(1/2)
Substituting the values of tan(1/4 + 2/9) and tan(1/2), we get:
tan(1/4) * tan(2/9) = 1/2 - 1/2
tan(1/4) * tan(2/9) = 0
Therefore, the correct option is 'D', i.e. tan(1/4) * tan(2/9) is equal to tan(1/2).
tan⁻1(1/4)+ tan⁻1(2/9) is equal toa)(1/2)cos⁻1(3/5)b...
By the formula ,
tan^-1(x) + tan^-1(y) = tan^-1 (x+y)/1-xy
when comparing ,
x= 1/4 and y= 2/9
substitute the values of x and y in the formula to get the answer