Addition of angles and multiple angle formulas

$\rhd$ Angle addition formulas (11:06) Formulas for $\sin(a\pm b)$ , $\cos(a\pm b)$ , $\cos(2a)$ , $\sin(2a)$ .
$\rhd$ Using the cosine angle addition formula (5:13) Given a right triangle $\Delta ABC$ and the lengths of its sides, find the cosine of $\angle ABC+60^o$ .
$\rhd$ Using the cosine double-angle formula (3:27) Given a right triangle $\Delta ABC$ and the lengths of its sides, find the cosine of $2\cdot\angle ABC$ .
$\rhd$ Finding trigonometric values using angle addition formulas (8:34) Find $\sin\left(\dfrac{7\pi}{12}\right)$ .
* Practice: Find trigonometric values using angle addition formulas. (4 problems)

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Addition of angles and multiple angle formulas

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The OpenLab at City Tech:A place to learn, work, and share

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