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Trigonometry — Mathematics STD 10 — Question

ICSE BoardEnglish MediumSTD 10MathematicsTrigonometry2 Marks
Question
Prove that $\cos \theta \sin (90^\circ - \theta ) + \sin \theta \cos (90^\circ - \theta ) = 1.$
✓

Answer

$LHS = \cos \theta \sin (90^\circ - \theta ) + \sin \theta \cos (90^\circ - \theta )$
$= \cos \theta . \cos \theta + \sin \theta . \sin \theta$
$= \cos^2\theta + \sin ^2\theta$
$= 1$
$= RHS$
Hence proved.

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