Which angle in the figure is a right angle? A. ECF B. C C. DCE D. DCF

The angle DCF is the right angle (D.).

Step-by-step explanation:

Usually, the right angles are marked with a small square, so if you see that, it means that is a 90º angle, no questions asked. :]

Answer A. says ECF, but that is only one of the two angles that add up to make the 90º angle.

Answer B. is not an angle at all. They should come with a slanted L and 3 letters to indicate an angle.

Answer C. says DCE, but that is just the other angle that adds up to make the 90º angle.

So that means Answer D. is the correct answer!

D. DCF

Step-by-step explanation:

A right angle or 90 degree angle angle is denoted by a small square where two line segments or rays meet to create an angle.

Angle ECF is inside of the right angle, but it only makes up part of it.

Angle C is not an angle.

Angle DCE is also inside of the right angle, but only makes up part of it.

Angle DCF is the angle with a small square inside of it. Therefore, it must be the right angle.

D. DCF is the correct answer.

step-by-step explanation:

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the solution of the equation is 2.23 ⇒ answer b

step-by-step explanation:

* lets revise the meaning of exponential function

- the form of the exponential function is y = ab^x, where a ≠ 0, b > 0 ,  

  b ≠ 1, and x is any real number

- it has a constant base b

- it has a variable exponent x

- to solve an exponential equation, take the log or ln of both sides,  

  and solve for the variable

* lets solve the problem

∵

- the base is 7 and the exponent is x

- insert ㏑ in both sides

∴

- use the rule

∴ x ㏑(7) = ㏑(77)

- to find x divide both sides by ㏑(7)

∴

* the solution of the equation is 2.23 to the nearest 2 decimal places