Question about trigonometry!

[MedicalStudent8]

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I know that trigonometry is on the DAT test, so perhaps someone here can help me... My question is, why, when using the Product-to-sum Identities, do you not have to use the cosine/sine of a sum/difference identities first. For example, why is sin(2x - 1)cos(x + 1) simply rewritten using the Reduction Theorem without first using the Cosine of a Difference and the Sin of the Difference formulas? 😕 Thanks if anyone can help me out with that!

P.S. How much trig is on the DAT test (like percentage wise)? I ask because for whatever reason, the trigonometry part of my brain is apparently missing.

 

[craptastic]

we need to memorize the reduction formulas too??? like sum-> product and product->sum? This QR test is worse than a trig class.

 

[MedicalStudent8]

we need to memorize the reduction formulas too??? like sum-> product and product->sum? This QR test is worse than a trig class.

I don't know, but I'd rather be safe than sorry. 🙁 Geeze, I hope not.... This test really sux. lol

 

[MedicalStudent8]

Bump?

 

[smec]

Bump?

Just flip to the front or end page of any pre-calculus or pre-college algebra book and you will find all essential trig identities needed to be known for DAT's QR.