Question

Pleaseee help guys:(

Answer 1

≈0.524094
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Answer 2

Answer:

$-\sqrt{3} /2$

Step-by-step explanation:

Note that this looks like the identity:

cos(A + B) = cosAcosB - sinAsinB.

In this case, A = π/12 and B = 3π/4. So, we can say that the given equation:

cos(π/12)cos(3π/4) - sin(π/12)sin(3π/4) = cos(π/12 + 3π/4) = cos(π/12 + 9π/12) = cos(10π/12) = cos(5π/6)

Ah, now we have a trigonometry problem we can easily solve!

cos(5π/6) = -cos(π/6) = -(√3)/2

Hope this helps!