SOLUTION: If a person bends at the waist with a straight back making an abgle of theta degrees with the horizontal, the the force F exerted on the back muscles can be modeled by the equation

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Question 188286: If a person bends at the waist with a straight back making an abgle of theta degrees with the horizontal, the the force F exerted on the back muscles can be modeled by the equation...
F = .6Wsin(theta + 90degrees)/ sin 12
where W is the weight of the person.
Use an identity to show that F is approximately equal to 2.9W cos theta.
I had no clue how to do this one.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
One of the many trig identities is sin%28A%2BB%29=sin%28A%29cos%28B%29%2Bcos%28A%29sin%28B%29



... Start with the given equation.


... Use the identity given above


... Evaluate the cosine of 90 degrees to get 0. Evaluate the sine of 90 degrees to get 1.


... Multiply


... Simplify


... Evaluate the sine of 12 degrees to get approximately 0.2079


... Divide 0.6%2F0.2079 to get roughly 2.8858


... Round to the nearest tenth