Question

Sin square 72 degree minus cos square 30 degree equal to under root 5 minus 1 by 8

Answer 1

Answer:

Find value of Sin72° first and after that prove the equation.

Step-by-step explanation:

sin²72°-cos²30°=√5-1/8

sin²72°=√5-1/8 + 3/4

=2.23-1/8+3/4

=1.23/8+3/4

=1.23+6/8

=7.23/8

(sin72°)²=7.23/8

sin72°=√7.23/8

sin72°=0.95

so ,here we found out value of sin 72°.

Now,

sin²72°-cos²30°=(0.95)²-(√3/2)²

=0.9025-3/4

=9025/10000-3/4

=√5-1/8. <-----proved

Hope this will help you to understand the concept of proving this type of questions.