Posted by **Abby** on Tuesday, February 23, 2010 at 7:00pm.

1) Solve the equation

sinx(sinx+1) = 0

I am having trouble with the first step. Could I do sin x^2 + 1 =0?

- Pre-cal -
**MathMate**, Tuesday, February 23, 2010 at 8:31pm
Using distributive property of multiplication over addition:

p(p+1)=x²+x

If p=sin(x), then

sin(x)(sin(x)+1)=sin²(x)+sin(x)

However, this particular problem does not require the expression to be expanded.

In fact, if

p(p+1)=0, it means that either p=0, or p+1=0.

Substitute p=sin(x), we get:

sin(x)=0 .......(1) or

sin(x)+1=0.......(2)

Solve for x in each of the two cases. The answer is the union of the two sets of answers.

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