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Question -

Find the equation of the line whose perpendicular distance from the origin is 4 units and the angle which the normal makes with the positive direction of x–axis is 15°.



Answer -

Given:

p = 4, α = 15°

The equation of theline in normal form is given by

We know that, cos15° = cos (45° – 30°) = cos45°cos30° + sin45°sin30°

Cos (A – B) = cos Acos B + sin A sin B

So,

And sin 15 = sin(45° – 30°) = sin 45° cos 30° – cos 45° sin 30°

Sin (A – B) = sin Acos B – cos A sin B

So,

Now, by using theformula,

x cos α + y sin α= p

Now, substitute thevalues, we get

(√3+1)x +(√3-1) y =8√2

The equation of linein normal form is (√3+1)x +(√3-1) y = 8√2.

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