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3 years ago

PLEASE HELP ME!!! I don’t understand

Mathematics

2 answers:

s344n2d4d5 [400]3 years ago

8 0

Answer:

see explanation

Step-by-step explanation:

Using the addition formula for cosine

cos(x ± y) = cosxcosy ∓ sinxsiny

and exact values

sin45° = cos45° = $\frac{\sqrt{2} }{2}$

c0s30° = $\frac{\sqrt{3} }{2}$ , sin30° = $\frac{1}{2}$

Express cos15° = cos(45 - 30 )°, then

cos(45 - 30)°

= cos45°cos30° + sin45°sin30°

= $\frac{\sqrt{2} }{2}$ × $\frac{\sqrt{3} }{2}$ + ( $\frac{\sqrt{2} }{2}$ × $\frac{1}{2}$ )

= $\frac{\sqrt{6} }{4}$ + $\frac{\sqrt{2} }{4}$

= $\frac{\sqrt{6}+\sqrt{2} }{4}$ ← exact value

ElenaW [278]3 years ago

6 0

Answer:

√6 + √2

= --------------

Step-by-step explanation:

15° = 45° - 30°

cos(15) = cos(45 - 30)

=cos(45) × cos(30) + sin(45) × sin(30)

= 1/√2 × (√3)/2 + 1/√2 × 1/2

(√3) + 1

= --------------

2√2

(√3) + 1 √2

= -------------- x ---------

2√2 √2

√6 + √2

= --------------

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