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Trigonometry — Mathematics STD 10 — Question

ICSE BoardEnglish MediumSTD 10MathematicsTrigonometry2 Marks
Question
Prove that identity:
$\frac{\sec A-1}{\sec A+1}=\frac{1-\cos A}{1+\cos A}$
✓

Answer

$\text { LHS }=\frac{\sec A-1}{\sec A+1}$
$=\frac{\frac{1}{\cos A}-1}{\frac{1}{\cos A}+1}$
$=\frac{\frac{1-\cos A}{\cos A}}{\frac{1+\cos A}{\cos A}}$
$=\frac{1-\cos A}{1+\cos A}$
$= RHS$
Hence proved.

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