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Use the sum and difference identities to rewrite the following expression as a trigonometric function of a single number.COS(30°) cos(45") + sin(30°)sin(45)

Use the sum and difference identities to rewrite the following expression as a trigonometric-example-1
User Bethany
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1 Answer

16 votes
16 votes

Remember that


\cos (a+b)=\cos a\cdot\cos b+\sin a\cdot\sin b

therefore

a=30 degrees

b=45 degrees

so


\cos (30^o+45^o)=\cos (75^o)=\cos 30^o\cdot\cos 45^o+\sin 30^o\cdot\sin 45^o

User Gerco Dries
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