Advanced Functions

How would I do this:

-cos(90-x)

I know you would use the compound angle formula and I know how to do it but when you have -cos do you replace the cos with the negative?

so for example

-cos90(-cosx) + sinx(sin90)

  1. 👍 0
  2. 👎 0
  3. 👁 53
asked by Mandy
  1. co-sine means sine of co-mplimentary angle.

    so, cos(90-x) = sin(x)
    and your function is just -sin(x)

    Or, you can apply the difference formula, but that is done before the negative

    -[cos(90-x)]
    = -[cos90cosx+sin90sinx]
    = -sinx

    1. 👍 0
    2. 👎 0
    posted by Steve

Respond to this Question

First Name

Your Response

Similar Questions

  1. trigonometry

    Use a compound angle formula for cosine to show that cos2x = cos^2x - sin^2x

    asked by Anonymous on November 2, 2009
  2. pre-calc

    simplfy the expression by double angle formula or a half angle formula. cos^2(x/2)-sin^2(x/2) 2sin(x/2)cos(x/2)

    asked by Amanda on April 22, 2012
  3. Trigonometry - Identities

    If tan 2x = - 24/7, where 90 degrees < x < 180 degrees, then find the value of sin x+ cos x. I applied various identities and tried manipulating the problem to get sin x + cos x = sin(arctan(-24/7)/2) + cos(arctan(-24/7)/2) I also

    asked by Sam on November 14, 2013
  4. Trig

    If cosx = 10/19 an pi < x < 2pi, find the exact value of cos x/2 Use the double angle formula. Cos 2Y= sin^2 Y - cos^2Y = 1-2Cos^2 Y. let y= x/2, and 2Y=x

    asked by Ashley on April 14, 2007
  5. math

    Find the exact value of cos 300 degrees. thanks guys cos 300 = 1/2 = 0.500 how do you know? I am supposed to show my work. You ought to know the rule on 30-60-90 triangles. If the hyp is 2, the shorter side is 1, and the longer

    asked by Bill on June 2, 2007
  6. Trig Help!

    Question: Trying to find cos π/12, if cos π/6 = square root 3 over 2, how to find cos π/12 using DOUBLE angle formula? This is what I got so far.. cos 2(π/6) = cos (π/6 + π/6) = (cos π/6)(cos π/6) - (sin π/6)(sin π/6) =

    asked by Anonymous on April 27, 2012
  7. General Chemistry

    An unknown compound has a formula of CxHyOz. You burn 0.1523 g of the compound and isolate 0.3718 g of CO2, and 0.1522 g of H2O. What is the empirical formula of the compound? If the molar mass is 72.1 g/mol what is the molecular

    asked by Jashmid on December 8, 2010
  8. Chemistry

    Please check my answers for the following questions. THANK YOU. 1) The empirical formula of a compound that is 25.9% nitrogen and 74.1% oxygen is.... ANSWER: N2O 2) empirical formula of a compound that consists of 4.80 grams of

    asked by anonymous on August 2, 2007
  9. trig

    Use a compound angle formula for sine to show that sine2(theta) = 2sine(theta)cos(theta)

    asked by Anonymous on November 1, 2009
  10. Pre-Cal

    1) Verify the identity cos^2 B - sin^2 B = 2 cos^2 B -1 I know that cos^2 B - sin^2 B = 2 cos^2 B -1 by the double angle formula but I do not know how to show this.

    asked by Hannah on February 27, 2010

More Similar Questions