Question

hey ppl

Solve this!!

Answer only if u know! ​

Answer 1

Step-by-step explanation:

We know that:

cos A = 1 - 2 sin² (A/2)

⇒ cos A - 1 = -2 sin² (A/2)

⇒ 1 - cos A = 2 sin² (A/2)

⇒ 2 sin²(A/2) = 1 - cos A

$\Longrightarrow sin^2 22\frac{1}{2} = 1 - cos 45$

$\Longrightarrow sin^2 22\frac{1}{2} =\frac{1-cos45}{2}$

$\Longrightarrow sin^2 22\frac{1}{2} =\frac{1-\frac{1}{\sqrt{2}}}{2}$

$\Longrightarrow sin \ 22\frac{1}{2} =\sqrt{\frac{1}{2}(1-\frac{1}{\sqrt{2}})}$

$\Longrightarrow sin \ 22\frac{1}{2} = \sqrt{\frac{\sqrt{2}-1}{2\sqrt{2}}}$

$\Longrightarrow sin \ 22\frac{1}{2} = \frac{1}{2}\sqrt{2-\sqrt{2}}$

Hope it helps!

Answer 2

That is. Cos 2A= 1–2sin^2 A

Cos 45°=1–2sin^2 45÷2

1–1÷√2 = 2sin^2 45÷2

√2÷2√2–1÷√2= sin^2 45°÷2

Therefore sin 45÷2 = √2–1÷2√2 ka whole square root