Question

very short anser type question
find the value of cos² 65° + cos² 25°

Answer 1

Answer:

1

Step-by-step explanation:

cos² 65° + cos² 25°

= cos² 65° + sin²(90°-25°)

= cos² 65° + sin² 65°

= 1 [ sin² ∅ + cos²∅ = 1 ]

Answer 2

Question

Very short anser type question

Find the value of cos² 65° + cos² 25°.

Answer

cos² 65° + cos² 25°

$\mathfrak{cos^{2}65 + cos {}^{2}25 }$

$\nrightarrow\mathfrak{cos^{2}65° + cos {}^{2}(90° - 65°) }$

$\nrightarrow\mathfrak{cos^{2}65° + sin {}^{2} 65° }$

$\nrightarrow\mathfrak{1[cos^{2}\theta + sin {}^{2}\theta]}$

$\nrightarrow\mathfrak{1×1}$

$\nrightarrow\mathfrak{1}$

Some important formulas

Trigometric Identities

Sin²A + Cos²A = 1

1 +Tan²A = Sec²A

1+ Cot²A = Cosec²A

Complementary Angle

Sin $\theta$ = Cos ( 90 - $\theta$)

Cos $\theta$ = Sin ( 90 - $\theta$)

Tan $\theta$ = Cot ( 90 - $\theta$)

Cosec $\theta$ = Sec (90 - $\theta$)

Sec $\theta$ = Cosec (90 - $\theta$ )

Cot $\theta$ = Tan (90- $\theta$ )