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Mathematics - 3D-Coordinate Geometry Question with Solution | TestHub

Mathematics3D-Coordinate GeometryMiscellaneous/MixedMedium2 minQB

MathematicsMediumnumerical

Lines $b x = 1 - cy, b z = 1$ and $b x = 2 + a y, b z = 3 + cy$ are perpendicular, where $a, b, c$ are side lengths of a triangle. Find the minimum value of $cos B$ .

Answer:

0.50

Solution:

Perpendicularity gives $b^{2} = a c$ . Hence $cos B = (a^{2} + c^{2} - a c) / (2 a c) = \frac{1}{2} (a / c + c / a) - \frac{1}{2} \geq \frac{1}{2}$ .

Stream:JEESubject:MathematicsTopic:3D-Coordinate GeometrySubtopic:Miscellaneous/Mixed

⏱ 2mℹ️ Source: QB

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