Q. Prove the identities with all angles acutei. secA1+secA=1−cosAsin2A
Rewrite using secant definition: Rewrite the left side of the equation using the definition of secant: secA=cosA1. So, (1+secA)/(secA) becomes (1+cosA1)/(cosA1).
Combine terms in numerator: Combine the terms in the numerator: 1+cosA1=cosAcosA+1.
Divide numerator by denominator: Now, divide the combined numerator by the denominator: (cosAcosA+1)/(cosA1).
Simplify division by reciprocal: Simplify the division by multiplying by the reciprocal of the denominator: (cosA+1)/cosA×cosA/1.
Cancel out cosA terms: The cosA terms cancel out, leaving us with cosA+1.
Use Pythagorean identity: Now, let's look at the right side of the equation: 1−cosAsin2A.
Substitute identity into right side: Use the Pythagorean identity sin2A=1−cos2A.
Factor numerator as difference of squares: Substitute the identity into the right side of the equation: (1−cos2A)/(1−cosA).
Cancel out (1−cosA) terms: Factor the numerator as a difference of squares: 1−cosA(1−cosA)(1+cosA).
Final expression on both sides: The (1−cosA) terms cancel out, leaving us with 1+cosA.
Final expression on both sides: The (1−cosA) terms cancel out, leaving us with 1+cosA.We now have the same expression on both sides of the equation: cosA+1.
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