Math Problem Statement

In triangle PQR, PR = 12 cm, angle R = 40° and the area is 32 cm². Find length QR. In triangle PQR, QR = 8 mm, angle R = 35° and the area is 12 mm². Find length PR. In triangle ABC, a = 5.2 cm, angle B = 55° and the area is 15 cm². Find length c. In triangle ABC, a = 6.8 cm, angle B = 100° and the area is 28 mm². Find length c.

Solution

Here is how to solve these problems systematically:


32 (a)

Given:

  • PR=12cmPR = 12 \, \text{cm},
  • R=40\angle R = 40^\circ,
  • Area = 32cm232 \, \text{cm}^2.

Find: QRQR.

Using the formula for the area of a triangle: Area=12absinC\text{Area} = \frac{1}{2} \cdot a \cdot b \cdot \sin C where aa and bb are two sides, and CC is the included angle.

Here, PRPR acts as bb, and QRQR is aa. Therefore: 32=1212QRsin(40)32 = \frac{1}{2} \cdot 12 \cdot QR \cdot \sin(40^\circ)

Rearranging for QRQR: QR=23212sin(40)QR = \frac{2 \cdot 32}{12 \cdot \sin(40^\circ)}


32 (b)

Given:

  • QR=8mmQR = 8 \, \text{mm},
  • R=35\angle R = 35^\circ,
  • Area = 12mm212 \, \text{mm}^2.

Find: PRPR.

Using the same formula: 12=128PRsin(35)12 = \frac{1}{2} \cdot 8 \cdot PR \cdot \sin(35^\circ)

Rearranging for PRPR: PR=2128sin(35)PR = \frac{2 \cdot 12}{8 \cdot \sin(35^\circ)}


33 (a)

Given:

  • a=5.2cma = 5.2 \, \text{cm},
  • B=55\angle B = 55^\circ,
  • Area = 15cm215 \, \text{cm}^2.

Find: cc.

Using the same formula: 15=125.2csin(55)15 = \frac{1}{2} \cdot 5.2 \cdot c \cdot \sin(55^\circ)

Rearranging for cc: c=2155.2sin(55)c = \frac{2 \cdot 15}{5.2 \cdot \sin(55^\circ)}


33 (b)

Given:

  • a=6.8cma = 6.8 \, \text{cm},
  • B=100\angle B = 100^\circ,
  • Area = 28mm228 \, \text{mm}^2.

Find: cc.

Using the same formula: 28=126.8csin(100)28 = \frac{1}{2} \cdot 6.8 \cdot c \cdot \sin(100^\circ)

Rearranging for cc: c=2286.8sin(100)c = \frac{2 \cdot 28}{6.8 \cdot \sin(100^\circ)}


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Math Problem Analysis

Mathematical Concepts

Geometry
Trigonometry
Area of a Triangle

Formulas

Area = 0.5 * a * b * sin(C)

Theorems

Law of Sines (implied in trigonometric relationships)

Suitable Grade Level

Grades 10-12