kitty<3

Para cuál problema?

a+[ ( -2a + b ) - ( -a +b -c) + a ]

= a + (-2a + b - -a - b - - c + a)

= a + ( -2a + b + a - b + c + a)

= a -2a + b + a - b + c + a

= a + c

Juana tiene 39.
Ella recibe 357 + 127 figuritas, = 484 figuritas.

En total, ella tiene 39 +484 figuritas,
Es 523 figuritas.

Escriba 899/30 en la calculadora: $${\frac{{\mathtt{899}}}{{\mathtt{30}}}} = {\mathtt{29.966\: \!666\: \!666\: \!666\: \!666\: \!7}}$$

Es un fracción.

Escriba atan(9.9) 

= $$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\mathtt{9.9}}\right)} = {\mathtt{84.232\: \!111\: \!102\: \!086^{\circ}}}$$

You put one digit before the decimal point and all the rest after it.  Then multiply the number by 10 to the power of however many places you moved the decimal point to the left. So for this problem, since you moved the decimal point 5 places to the left:

$${\mathtt{425\,950}} = {\mathtt{4.2595\times 10^{5}}}$$

Hello sally1,

The equation for a circle is: (x-h)² + (y-k)² = r² 

(h, k) is the center.

So the center of the circle will be halfway between the endpoints of the diameter (the midpoint). Use the Midpoint Formula: [(x₁+x₂)/2 ,  (y₁+y₂)/2]

= [(-1 + 5)/2 , (1 + 9)/2]

= (2, 5)

So the equation so far is: (x-2)² + (y-5)² = r²

Now find the radius, which is the diameter divided in half. 

Use the Distance Formula to find the diameter:

Plug in the endpoints of the diameter: d = sqrt[(5 - -1)² + (9- 1)²]

Simplify.

d = sqrt( 36 + 64)

d = sqrt(100)

d = 10

Half of that = radius = 5

Radius squared = 25

So the final equation: (x-2)² + (y-5)² = 25

Complemetary angles are angles that add up to 90 degrees.

So you would set up the equation:

2x + 6x = 90

8x = 90

x = 11.25

First, you would need to know the angle the sin is referring to, such as sin(30) or sin(56). Then you could just enter it into a calculator and multiply it by 0.6

Unless you mean sin(0.6), which is  $$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}{\left({\mathtt{0.6}}^\circ\right)} = {\mathtt{0.010\: \!471\: \!784\: \!116}}$$ in degree mode and 0.564642473395 in radian mode.