Tuesday

September 30, 2014

September 30, 2014

Posted by **Anonymous** on Saturday, November 7, 2009 at 10:19pm.

sinx = (square root of) 1 - cos^2x

is not an identity

- Math -
**Reiny**, Saturday, November 7, 2009 at 10:40pmAll we need is one counterexample to show it is not an identity.

let x = 210º

LS = sin 210 = -1/2

RS = √(1- cos^2 (210º))

= √(.25)

= 1/2

So there!

**Answer this Question**

**Related Questions**

Math - 1) evaluate without a calculator: a)sin(3.14/4) b) cos(-3(3.14)/4) c) ...

Trig - prove the identity (sinX)^6 +(cosX)^6= 1 - 3(sinX)^2 (cosX)^2 sinX^6= ...

Mathematics - Trigonometric Identities - Prove: sin^2x - sin^4x = cos^2x - cos^...

Math simplifying mixed radicals - Please help me simplify these following mixed ...

Pre-calc - prove the identity: (cosx)(tanx + sinx cotx)=sinx+cos(squared)x i ...

Math simplifying mixed radicals - Please help me simplify these following mixed...

Math - Pre- Clac - Prove that each of these equations is an identity. A) (1 + ...

Math (trigonometric identities) - I was given 21 questions for homework and I ...

Trig........ - I need to prove that the following is true. Thanks (cosx / 1-sinx...

Pre-Calc : Verify the Identity - Verify the Identity: sin(x+π)/cos(x+3π...