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January 28, 2015

January 28, 2015

Posted by **AwesomeGuy** on Sunday, February 10, 2013 at 1:54am.

1.) SIN²x(CSC²x-1)

2.) COT x SEC X

3.) COS²[(π/2)-x]/COS X

(Note: These mathematical problems are somewhat tricky, but useful for students as of learning how to their fundamental identities. Let's enjoy solving these problems!)

- Trigonometry -
**Reiny**, Sunday, February 10, 2013 at 7:28amYou have no equations to solve, you probably meant "simplify the expressions"

1. sin^2 x (1/sin^2 x - 1)

= 1 - sin^2 x

= cos^2 x

2. (cosx/sinx) (1/cosx)

= 1/sinx

= cscx

3. recall the property of complementary trig ratios, that is...

sin(π/2 - x) = cosx and cos(π/2 - x) = sinx

sec(π/2 - x) = cscx and .....

tan(π/2 - x) = cotx

notice the names:

sine --co-sine or cosine

tangent -- co-tangent or cotangent

secant --- co-secant or cosecant

e.g. sin (90° - 20°) = sin 70° = cos20°

so your question:

COS²[(π/2)-x]/COS X

= sin^2 x / cosx

= (sinx)(sinx/cosx)

= sinx tanx

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