The value of sin 20° cos 70° + s

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Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

The value of sin 20° cos 70° + sin 70° cos 20° is :

Options:

$\frac{1}{\sqrt{2}}$

Correct Answer:

Explanation:

sin20° cos 70° + sin70° cos 20°

We know,

sinA = cosB Iff A + B = 90°

Similarly sin20° = cos70°

So,

= sin20° .sin 20° + cos20°. cos 20°

= sin²20° + cos²20°

= 1 { sin²θ + cos²θ = 1 }