$cos2A=cos(A+A)=cos^2A-sin^2A\\sin2A=sin(A+A)=2sinAcosA\\sin4A=sin(2A+2A)=2sin2Acos2A=2(2sinAcosA)(cos^2A-sin^2A)=4sinAcos^3A-4cosAsin^3A\\secA=\frac{1}{cosA}$

Therefore:

$\frac{1}{4}sin4AsecA = \frac{1}{4}( 4sinAcos^3A-4cosAsin^3A)\frac{1}{cosA}\\= sinAcos^3A-cosAsin^3A(\frac{1}{cosA} )\\=sinAcos^2-sin^3A\\=sinA(cos^2A-sin^2A)\\But\ cos^2A-sin^2A=cos2A\\Therefore:sinA(cos^2A-sin^2A)=sinAcos2A\\\frac{1}{4}sin^4Acos2A=sinAcos2A$

4 0

2 years ago

Mr. Chen has heard about a Medical Savings Account (MSA), but wants to know if it is just about saving money, or if he will get

stepladder [879]

Answer:

A medical savings account (MSA) refers to a medical savings account program, generally associated with self-employed individuals, in which tax-deferred deposits can be made for medical expenses. Withdrawals from the MSA are tax-free if used to pay for qualified medical expenses.

Explanation:

Mr. Chen, Medical Savings Account, MSA does not involve insurance coverage. It covers only medical expenses.

8 0

2 years ago