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Trigonometrical Identities — Mathematics STD 10 — Question

ICSE BoardEnglish MediumSTD 10MathematicsTrigonometrical Identities2 Marks
Question
Find $A$, if $0^\circ \leq A \leq 90^\circ $ and $\cos^2A - cosA = 0$
✓

Answer

$\cos^2A - cosA = 0$
$\Rightarrow cosA (cosA - 1) = 0$
$\Rightarrow cosA = 0 or cosA = 1$
We know $\cos 90^\circ = 0$ and cos $0^\circ = 1$
Hence, $A = 90^\circ $ or $0^\circ$

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