# 3 on Pretest
Does anyone have an idea for # 3 on the pretest. I am pretty stuck. Thanks
posted by battlejoe18 at 9:41 PM
Blog for students in Mr. Karafiol's Period 4 Precalculus BC class to talk about math, learning math, etc.
posted by battlejoe18 at 9:41 PM
5 Comments:
sure. turn the stuff inside the tan( ) into an angle (lets call it w). so arcsin(2x-1) = w. This means that sin(w) = 2x-1. You can then draw a triangle with a sine of 2x-1... the side opposite angle w will equal 2x-1 and the hypotenuse will equal 1. If you use the Pythagorean theorem, you'll find that the third side of the triangle equals sqrt(1-(2x-1)^2). Now you know both sin(w) and cos(w) (which is that sqrt value you just found). Since the original expression was tan(arcsin(2x-1)) and we called arcsine(2x-1) "w," the original expression is tan(w), which is just sin(w) over cos(w).
Hope that didn't make things moe confusing.
muchas gracias! now i should remember
While we're at it, how do you do #11? I can't start a new thread.
the best advice i have is to set theta equal to tan(44/x)-tan(20/x). Notice that the billboard is 24 ft wide, and then add the distance from point a to the edge of the board. this way u'll find the distance from a to the spotlight by using tan.
still need help becoming a member of this blog. i have a gmail account. how di dyou all do it?
isabel
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