# Find the value of 2sin(alpha)*cos(alpha)

Trigonometry equalities, inequalities and expressions - sin, cos, tan, cot

### Find the value of 2sin(alpha)*cos(alpha)

Let's $$sin \alpha + cos \alpha = a$$
Find the value of the expression: $$2sin\alpha cos\alpha$$
sin cos

### Re: Find the value of 2sin(alpha)*cos(alpha)

if sinx+cosx=a than $$(sinx+cosx)^2=a^2$$
$$sin^2x+cos^2x +2sinxcosx=a^2$$
$$2sinxcosx=a^2-1$$
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### 1 - sin2x / 1 + sin2x

Simplify the trigonometric expression:
$$\frac{1 - sin2x }{1 + sin2x }$$

sin cos

### Re: 1 - sin2x / 1 + sin2x

sin cos wrote:Simplify the trigonometric expression:
$$\frac{1 - sin2x }{1 + sin2x }$$
= (1-2sinx*cosx)/(1+2sinx*cosx)=(1-a*a+1)/(1+a*a-1)=(2-a*a)/a*a
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