Posted by **May** on Monday, January 11, 2010 at 7:15pm.

Hi, could someone explain to me how to use a counterexample in trig to prove whether something is either an identity or equation?

For ex. how would you do that with this question?

sec^2x-tan^2x= cos x

- Math- gr.12 Trig. -
**Marth**, Monday, January 11, 2010 at 8:13pm
A counterexample is simply any instance that disproves the statement.

For example, try using x = pi/4. Note that this is NOT the only correct answer.

- Math- gr.12 Trig. -
**May**, Monday, January 11, 2010 at 8:19pm
Would I substitute the same number to both sides?

## Answer this Question

## Related Questions

- Prove trig identity - Prove the following trigonometric identity: (sec^2x-1)(csc...
- trig - Prove the following trig identity: 1 + sinx = sinx(1+cscx)
- math - could someone please refresh my memory of the basic trig functions? ex) ...
- ah trig help - use an apropriate sum or difference indentity to prove the double...
- trig - prove the trig identity cos(4x) = 2-sec^2(2x)/sec^2(2x)
- Trig - Prove the trig identity cos(4x)=2-sec^2(2x)/sec^2(2x)
- Trig - Prove the trig identity cos(4x)=2-sec^2(2x)/sec^2(2x)
- Math - Required to Prove the following trig identity: (cos2x)^2 + (sin2x)^2 = 1
- Trig - Prove that the equation is an identity: cot4theta - csc4theta = -cot sq ...
- Trigonometry/Geometry - Inequalities - Let a, b, and c be positive real numbers...

More Related Questions