Question

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高二數學 三角函數

(Sino-Coso =
5
→Sing=
7
Cose
5
5
Sin 2
gia (S)
5
27 sin $22.5° + sin 67.5° + sin 112.5° + sin 157.5° =
0
11
Sin 12.5 = Cost 22,5 Sinf 157.5° = Cost 61,5
76382
95232
3
類 28 若sin20:
Esin + cos 0 =
5
Sin 20 =
3
=25ing Coso
5
N
1+ Cos

Answer 1

✨ คำตอบที่ดีที่สุด ✨

qn

sin⁴θ + cos⁴θ
= sin⁴θ + cos⁴θ + 2sin²θcos²θ - 2sin²θcos²θ
= ( sin²θ + cos²θ )² - ½ × 4sin²θcos²θ
= 1 - ½ ( 2sinθcosθ )²
= 1 - ½sin²2θ

sin⁴22.5° + sin⁴67.5° + sin⁴112.5° + sin⁴157.5°
= sin⁴22.5° + sin⁴67.5° + sin⁴67.5° + sin⁴22.5°
= 2 ( sin⁴22.5° + sin⁴67.5° )
= 2 ( sin⁴22.5° + cos⁴22.5° )
= 2 ( 1 - ½sin²45° )
= 2( 1 - ½ × ½ )
= 2 × ¾
= 3/2

qn

sin⁴θ + cos⁴θ
= 1 - ½sin²2θ
= 1 - ½(-3/5)²
= 41/50

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