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2 years ago

Angles A and B are located in the first quadrant such that sinA= 7/25 and cosB = 5/13. Determine the exact value for cos (A-B).

Mathematics

1 answer:

fomenos2 years ago

8 0

Answer:

204/325

Step-by-step explanation:

You can work this a couple of ways. We expect you are probably expected to use trig identities.

cos(A) = √(1 -sin²(A)) = 24/25

sin(B) = √(1 -cos²(B)) = 12/13

cos(A -B) = cos(A)cos(B) +sin(A)sin(B) = (24/25)(5/13) +(7/25)(12/13)

= (24·5 +7·12)/325

cos(A -B) = 204/325

The other way to work this is using inverse trig functions. It is necessary to carry the full calculator precision if you want an exact answer.

cos(A -B) = cos(arcsin(7/25) -arccos(5/13)) = cos(16.2602° -67.3801°)

= cos(-51.1199°) ≈ 0.62769230 . . . . (last 6 digits repeating)

The denominators of 25 and 13 suggest that the desired fraction will have a denominator of 25·13 = 325, so we can multiply this value by 325 to see what we get.

325·cos(A-B) = 204

so, the exact value is ...

cos(A -B) = 204/325

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What is the sum of all of the four-digit positive integers that can be written with the digits 1, 2, 3 and 4 if each digit must

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Answer with explanation:

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3 years ago

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GuDViN [60]

Answer:

vertex = (0, -4)

equation of the parabola: $y=3x^2-4$

Step-by-step explanation:

Given:

y-intercept of parabola: -4
parabola passes through points: (-2, 8) and (1, -1)

Vertex form of a parabola: $y=a(x-h)^2+k$

(where (h, k) is the vertex and $a$ is some constant)

Substitute point (0, -4) into the equation:

$\begin{aligned}\textsf{At}\:(0,-4) \implies a(0-h)^2+k &=-4\\ah^2+k &=-4\end{aligned}$

Substitute point (-2, 8) and $ah^2+k=-4$ into the equation:

$\begin{aligned}\textsf{At}\:(-2,8) \implies a(-2-h)^2+k &=8\\a(4+4h+h^2)+k &=8\\4a+4ah+ah^2+k &=8\\\implies 4a+4ah-4&=8\\4a(1+h)&=12\\a(1+h)&=3\end{aligned}$