Question Details

If y(x) satisfies the differential equation

( sin x ) d y d x + y cos x = 1

subject to the condition y(π/2) = π/2, then y(π/6) is

Options

A

0

B

𝜋/6

C

𝜋/3

D

𝜋/2

Correct Answer :

𝜋/3

Solution :

The correct option/answer is π3 (which corresponds to π/3).

Step-by-Step Explanation:

We are given the following first-order ordinary differential equation:
( sin x ) d y d x + y cos x = 1
Observe the left-hand side of this differential equation. By applying the product rule of differentiation, ddx(u·v)=udvdx+vdudx, we can see that the left-hand side is the exact derivative of the product ysinx:
d d x ( y sin x ) = ( sin x ) d y d x + y cos x

Therefore, we can rewrite the differential equation as:
d d x ( y sin x ) = 1

To solve for y, we integrate both sides with respect to x:
d d x ( y sin x ) d x = 1 d x
This simplifies to:
y sin x = x + C
where C is the constant of integration.

Next, we determine the constant C using the given boundary condition y(π/2)=π/2. This means that when x=π2, we have y=π2:
( π 2 ) sin ( π 2 ) = π 2 + C
Since sin(π/2)=1, this equation becomes:
π 2 = π 2 + C
Subtracting π2 from both sides gives:
C = 0

Substituting C=0 back into the general solution yields the particular solution:
y sin x = x
Which can be solved explicitly for y as:
y ( x ) = x sin x

Finally, we calculate y(π/6) by substituting x=π6:
y ( π 6 ) = π / 6 sin ( π / 6 )
Knowing that sin(π6)=12, we compute:
y ( π 6 ) = π / 6 1 / 2 = π 6 × 2 = π 3

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