Question

prove that (sin 72 +cos 18) (sin 72 - cos 18) = 0

Answer 1

Answer:

(sin72+cos18)(sin72-cos18)

sin²72-cos²18

[sin(90-18)]²-cos²18

cos²18-cos²18

=0

Answer

Answer 2

Answer:

Hey mate here is your answer..

Step-by-step explanation:

$(a + b) \: (a - b) \: = \: {a}^{2} - {b}^{2}$

The given question is in the firm of the above formula.

we know the values of sin75 and cos18 i.e.,

$sin75 \: = cos18 \: = \: \frac{ \sqrt{10 + 2 \sqrt{5} } }{4}$

Now by applying these values we can solve the given problem.

Hope it helps you... :-)

Thank you ... :-)