# trig

cotx = -2 and 0 less than or equal to x less than or equal to pi

Find sin2x and cos2x

How to get the answers of sin2x = -4/5, cos2x = 3/5?

1. 👍 0
2. 👎 0
3. 👁 105
1. If cot x = -2 and x is in the first or second quadrant, it must be in the second quadrant, with a horizontal (x') coordinate -2 times the vertical (y') coordinate. The cosine of x is 2/sqrt 5 and the sine is -1/sqrt 5. You get that from the Pythagorean theorem and the fact that you are in the second quadrant.

Sin 2x = 2 sin x cos x = 2*(-2)/5 = -4/5
Cos 2x = cos^2 x - sin^2 x = 4/5 - 1/5 = 3/5

1. 👍 0
2. 👎 0
posted by drwls

## Similar Questions

1. ### HS Calculus/math

Solve the equation cotx=4 in the interval 0

asked by dt on October 31, 2008
2. ### trig

Is y equal to cotx, tanx, cosx, or sinx if its graph is periodic with a period of 2pi, an amplitude equal to 1, and it passes through the origin?

asked by Cutie_27 on February 15, 2010
3. ### Math

1)A piano tuner uses a tuning fork. If middle C has a frequency of 264 vibrations per second, write an equation in the form d=sinw(t) for the simple harmonic motion. 2) Verify the identity tan^2X-cot^2X/tanX+cotX=tanX-cotX I'm not

asked by Lisa on October 9, 2006
4. ### trig

{tan^2x+cotx divided by tanx-cotx} is equal to {1 divided by sin^2x-cos^2x}

asked by stacey graham on March 26, 2010
5. ### random variables

For the standard normal random variable Z, compute the following probabilities. For the following problems, use four decimal places. 16. P (0 less than or equal to Z less than or equal .9) 17. P (-1.3 less than or equal to Z less

asked by Felicia on August 2, 2010
6. ### Math

1) When will the dependent variable in the equation y=√x+4-3 equal or exceed to 4? A) x > or equal to -0.17 B) x > or equal to 45 C) x > or equal to 48 D) x > or equal to 53 2) The function t=√d/16 models the time (t) in

asked by Tia on April 7, 2015
7. ### Calculus

Consider the function f(x)=6x-cos(x)+5 on the interval 0 is less than or equal to x, and x is less than or equal to 1. The Intermediate Value Theorem guarantees that there is a value c such that f(c)=k for which values of c and k?

asked by Anonymous on February 1, 2012
8. ### Math

Hi everyone, my name is Emerson. I was wondering if anybody could help me on a test. I'm stuck on some, but I think I know some others. Thank you! 1. Translate the phrase "nine more than two times a number" in to an algebraic

asked by Emerson on December 7, 2015
9. ### calculus

Consider the function f(x)=65x−cos(x)+2 on the interval 0 less than or equal to x less than or equal to 1. The Intermediate Value Theorem guarantees that there is a value c such that f(c)=k for which values of c and k? Fill in

asked by lauren on February 2, 2012
10. ### Trig

Verify that each of the following is an identity. tan^2x-sin^2x=tan^2xsin^2x I can get it down to cos^2 on the right, but cannot get it to work out on the left. secx/cosx - tanx/cotx=1 On the left I got down to 1-tan^2, but that

asked by Andrea on February 28, 2008
11. ### math

7. The tennis team is selling key chains as a fundraiser. If its goal is to raise is at least 180, how many key chains must it sell at \$2.25 each to meet that goal? Write and solve an inequality. a. 2.25k (greater than or equal

asked by john on October 18, 2016

More Similar Questions