if acos theta - bsin theta =c then prove that asin theta +bcostheta=+-√a²+√b²-√c²
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Answer:
Given :-
→ a cos∅ + b sin∅ = c ...(1) .
Now,
→ ( a cos∅ - b sin∅ )² + ( a sin∅ + b cos∅ )² .
= a²cos²∅ + b²sin²∅ - 2a sin∅ b cos∅ + a²cos²∅ + b²sin²∅ + 2a sin∅ b cos∅ .
= a²sin²∅ + a²cos²∅ + b²cos²∅ + b²sin²∅ .
= a²( sin²∅ + cos²∅ ) + b²( cos²∅ + sin²∅ ) .
= a² + b² . [ ∵ sin²∅ + cos²∅ = 1 ] .
Thus, ( a cos∅ - b sin∅ )² + ( a sin∅ + b cos∅ )² = ( a² + b² ) .
⇒ c² + ( a sin∅ + b cos∅ )² = ( a² + b² ) .
⇒ ( a sin∅ - b cos∅ )² = ( a² + b² - c² ) .
⇒ ( a sin∅ - b cos∅ ) = ±√( a² + b² - c² ) .
Hence, \sf \pink { (a \: { \sin }^{2} \theta - b \: { \cos }^{2} \theta ) = ± \sqrt{ {a}^{2} + {b}^{2} - {c}^{2} } }
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