Select all the true equations.
A. $\cos (15)=\sin (15)$
B. $\cos (75)=\sin (15)$
C. $\cos (75)=\cos (15)$
D. $\cos (15)=\sin (75)$
E. $\tan (15)=\tan (75)$

Answer

Expert–verified

Hide Steps

Answer

\boxed{\text{Final Answer: The true equations are B and D.}}

Steps

Step 1 ：Evaluate each equation using trigonometric functions:

Step 2 ：A. $\cos(15) = \sin(15)$ is False

Step 3 ：B. $\cos(75) = \sin(15)$ is True

Step 4 ：C. $\cos(75) = \cos(15)$ is False

Step 5 ：D. $\cos(15) = \sin(75)$ is True

Step 6 ：E. $\tan(15) = \tan(75)$ is False

Step 7 ：\boxed{\text{Final Answer: The true equations are B and D.}}