The sum of squares of intercepts on the axes cut off by the tangents to the curve \(\mathrm{x}^{(2 / 3)}+\mathrm{y}(2 / 3)=\mathrm{a}^{(2 / 3)}(\mathrm{a}>0)\) at \([(\mathrm{a} / 8),(\mathrm{a} / 8)]\) is \(2 .\) Thus a has the value. (a) 1 (b) 2 (c) 4 (d) 8

Short Answer

Expert verified
The value of \(a\) is 8 (Option d).

Step by step solution

01

Find the equation of tangent passing through the point

The equation of the given curve is \(x^\frac{2}{3} + y^\frac{2}{3}= a^\frac{2}{3}\). Now, to find the equation of tangents passing through the point \(\left( \frac{a}{8},\frac{a}{8} \right)\), we differentiate the curve equation with respect to \(x\), which gives us the slope of the tangent. \[ \frac{d}{dx} \left( x^\frac{2}{3} + y^\frac{2}{3} \right) = 0\] \[\frac{2}{3}x^{\frac{-1}{3}} + \frac{2}{3}y^{\frac{-1}{3}} \frac{dy}{dx} = 0\] Now, run the given point or coordinates \(\left( \frac{a}{8},\frac{a}{8}\right)\) through the equation. \[\frac{2}{3}\left(\frac{a}{8}\right)^{-\frac{1}{3}} + \frac{2}{3}\left(\frac{a}{8}\right)^{-\frac{1}{3}} \frac{dy}{dx} = 0\] Next, solve for the slope: \[\frac{dy}{dx} = -\frac{2x^\frac{-1}{3}}{2y^\frac{-1}{3}} = -\frac{x^\frac{-1}{3}}{y^\frac{-1}{3}}\] At the point \(\left( \frac{a}{8},\frac{a}{8} \right)\), the slope of the tangent is \(-1\). With the slope and the point on the tangent, we can now use the point-slope form to find the equation of the tangent: \[y - \frac{a}{8} = -1 \cdot \left(x - \frac{a}{8}\right)\]
02

Find Intercepts of tangent

Now, we'll find the x-intercept and y-intercept of the tangent line. For x-intercept, set y = 0: \[0 - \frac{a}{8} = -1 \cdot \left(x - \frac{a}{8}\right)\] For y-intercept, set x = 0: \[y - \frac{a}{8} = -1 \cdot \left(0 - \frac{a}{8}\right)\] Solving these equations will give us the intercept points
03

Calculate the sum of squares of intercepts

Now, we will calculate the sum of squares of intercepts and set it equal to 2: \[\left(\frac{a^2}{64}\right) + \left(\frac{a^2}{64}\right) = 2\] Solve the equation for \(a\) and find its value.
04

Solve for \(a\)

\[\frac{a^2}{32} = 2\] \[a^2 = 64\] \[a = \pm 8\] Since given that \(a > 0\), the correct answer is: \(a = 8\) Hence, the value of \(a\) is 8 (Option d).

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