3 years ago

-3x +2y= 4 4x-13y=5 solve by elimination

1 answer:

4 0

I am better at substitution, but you want to get the equations as similar as possible, but are the opposite, so you can cancel it out.

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Subtract.<br><br> −3 3/8−7/8<br><br> Enter your answer, in simplest form, in the box.

sp2606 [1]

Answer:

-4 1/4

Step-by-step explanation:

7 0

3 years ago

Use a half-angle identity to find the exact value of tan 22.5°.

dusya [7]

Answer:

$\sqrt{2} -1$

Step-by-step explanation:

22.5 degrees is half of 45 degrees (special angle for which we know exactly the value of all three basic trigonometric functions (sine, cosine, and tangent).

So we start recalling the formula for tangent of a half angle: $tan(\frac{\alpha }{2} )= \frac{1-cos(\alpha) }{sin(\alpha) }$

We need just the values of:

$sin(\alpha )=sin(45^o)=\frac{\sqrt{2} }{2}$

and of

$cos(\alpha )=cos(45^o)=\frac{\sqrt{2} }{2}$

to answer the question. Then, we use those values in the original formula for tangent of a half angle:

$tan(\frac{\alpha }{2} )= \frac{1-cos(\alpha) }{sin(\alpha) }\\tan(22.5^o)=\frac{1-\frac{\sqrt{2} }{2} }{\frac{\sqrt{2} }{2}} =\frac{2-\sqrt{2} }{\sqrt{2} } =\frac{2\sqrt{2}-2 }{2} =\sqrt{2} -1$