Find the exact value of cos(arcsin( one fourth for full credit, explain your reasoning. (2 points)

Hello from MrBillDoesMath!

sqrt(15)/4

Discussion:

The attachment shows a right triangle where arcsin(@) = 1/4. (The arcsin means find the angle whose sine is 1/4 as is done in the triangle.) The missing side, sqrt(15), shown in red, was determined by the Pythagorean theorem.

Then cos(@) = cos(arcsin(1/4)) =  sqrt(15)/4

Thank you,

MrB

step-by-step explanation:

equation

you are asked to write the equation

  expression = 0

using the given expression. when you do that, you have

  2x^2-2x-12 = 0

factoring

you can see that each of the coefficients is even, so a factor of 2 can be removed immediately.

  2(x^2 -x -6) = 0

if you multiply the binomials (x+a)(x+b), you get

  (x +a)(x +b) = x^2 +(a+b)x +ab

this tells you the coefficient of x is the sum of two factors of the constant term. here, that means -1 is the sum of two factors of -6. we want to know those factors so we can factor the trinomial.

  -6 = -1×6 = -2×3 = -3×2 = -6×1

the factor pair that sums to -1 is {-3, 2}, so our factorization is

  2(x -3)(x +2) = 0

solutions

the solutions to this equation are the values of x that make the product zero. a product is zero only when only of the factors of the product is zero. here, that means

  x - 3 = 0

  x = 3 . . . add 3 to both sides of the equation

or

  x +2 = 0

  x = -2 . . . add -2 to both sides of the equation

the solutions to the equation are x=3 or x=-2. both of these values of x satisfy the equation—they make it be true.

this may not be at all, but i use the same website you're using for school, and if i'm stuck doing one of these i try to look for it on the section.