<span>2r2 + 3s3 − r2 + 4t2 − r2
</span>
= 19
The answer to this is C. 72
Given:
The figure of a rhombus QRST.
To find:
A. The value of x.
B. The measure of angle RQP.
Solution:
A. We need to find the value of x.
We know that the diagonals of a rhombus are perpendicular bisectors. It means the angles on the intersection of diagonals are right angles.
[Right angle]
Divide both sides by 5.
Therefore, the value of x is 15.
B. We need to find the measure of angle RQP.
From the given figure, it is clear that

Putting
, we get



Therefore, the measure of angle RQP is 33 degrees.
Answer: see proof below
<u>Step-by-step explanation:</u>
Given: A + B + C = π and cos A = cos B · cos C
scratchwork:
A + B + C = π
A = π - (B + C)
cos A = cos [π - (B + C)] Apply cos
= - cos (B + C) Simplify
= -(cos B · cos C - sin B · sin C) Sum Identity
= sin B · sin C - cos B · cos C Simplify
cos B · cos C = sin B · sin C - cos B · cos C Substitution
2cos B · cos C = sin B · sin C Addition
Division
2 = tan B · tan C

<u>Proof LHS → RHS</u>
Given: A + B + C = π
Subtraction: A = π - (B + C)
Apply tan: tan A = tan(π - (B + C))
Simplify: = - tan (B + C)

Substitution: = -(tan B + tan C)/(1 - 2)
Simplify: = -(tan B + tan C)/-1
= tan B + tan C
LHS = RHS: tan B + tan C = tan B + tan C 