Question

find the value of cos (90°-theta)×sin theta +sin (90°-theta)×cos theta​

Answer 1

${\huge{\purple{\mathbb{\bold{ANSWER}}}}}$

=》 Let theta be ○ For ease of writing.

${\large{\blue{\bold{\underline{IDs\:Used:-}}}}}$

1. Cos (90-○) = Sin ○

2. Sin (90-○) = Cos ○

3. sin²○+cos²○ = 1.

${\large{\blue{\bold{\underline{Now,}}}}}$

=》 Cos(90-○)×Sin○ + Sin(90-○)×Cos○

= Sin○×Sin○ + Cos○×Cos○

{From IDs (1) and (2).}

= Sin²○ + Cos²○

${\large{\green{\boxed{\bold{=\:1.}}}}}$

{From id(3).}

${\large{\blue{\bold{\underline{Therefore, }}}}}$

Cos(90-○)×Sin○ + Sin(90-○)×Cos○ = 1.

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